So obviously this falls under Rule of Scary, but isn't it kind of odd that every single ghost you (the investigators) come across is homicidal? Maybe you and/or your team are playing as jerks—making fun of the ghost, being loud/noisy, swearing—but even if you're the nicest crew, and no matter who the ghosts were in life (leaving aside the demons), every single one of them immediately goes for the Neck Snap. It just seems strange that there isn't at least one ghost out there who just wants to be left alone, especially if you subscribe to the theory that ghosts are the result of unfinished business on Earth.
If anything were to be guessed from the general theme of ghosts spotted, from their painfully decayed appearance, love for flashing their old weapons to investigators and how potentially old and also malevolent attitude to being near people, it’s possible that the ghosts are kept on Earth through The Power of Hate. Whether it’s the pain of undeath making them lash out or possible previous lives as crooks and serial killers, the ghosts 'unfinished business' could very well just be a drive to hurt and kill people, or so overcome with painful emotion that they’re taking it out in the living. The latter is especially supported by how catching a ghosts attention with their real name or taunting them causes enough discomfort or frustration that they’ll generally try to make a move on the offender for it.
All this makes sense, it's just odd that the investigators only ever seem to run across the ghosts of crooks and serial killers—there's never any sweet little old lady ghost or cheerful child ghost. Out of universe, it makes sense—without a time limit of "solve this and get out before the ghost kills you and your teammates," the game loses its scary factor and its stakes—but in universe, this seems like very bad luck for the investigators, at the least.
Considering that the teams in Phasmophobia are sent as scouts in advance of an exorcism team which is what actually gets rid of the ghosts; it may be a case of Fridge Brilliance - the harmless ghosts, well, don't really harm anyone; so they may go completely unnoticed or are considered a non-priority by the company the players work for. Therefore, they only get sent on dangerous missions - to ghosts who drew attention by actually harming people.
Non-hostile ghosts also probably wouldn't require such a careful investigation before the exorcism; the exorcists can just take their time, narrowing down the possibilities at a more leisurely pace or even through trial and error, since the ghost isn't actively trying to kill them. An actively hostile ghost would put them on a much tighter schedule, since they've got to figure out what they're dealing with and perform the exorcism before they all die. In the case of a hostile ghost, separating the investigation and exorcism into two separate phases helps minimize the risks associated with the latter, since they can get in, do the exorcism, and get out as quickly as possible.
Tutorial mission does have a non-murderous ghost. This ghost will not attack the player, making them perfect training material. Of course, it also shows why game doesn't have non-hostile ghosts: they are boring.
Offering exorcism services to places nobody lives
So again, Rule of Scary, but I can totally see why there’d be a service who removes a ghostly presence from your home, but who's paying for the teams to go and investigate and draw out spirits in abandoned high schools and asylums? I can only see a ghost haunting places like those being a problem for the homeless, urban explorers and teens looking for cheap thrills in dusty old places, who I can’t imagine would pay well to exorcise a building they can just avoid anyways, unlike a home owner who has a ghost stalking and attacking them in their own home. At least with the prison I can imagine a perfectly good facility being checked out with a clean bill of health so it can be reused, but a derelict and haunted high school and asylum seems like a job for the demolitions team, whenever they’d get around to that anyways.
Probably because the ghosts themselves are murderous, anyone who has watched, basically, any haunted house horror film knows, that while abandoned buildings might not be used for their purpose anymore, people still do "use" them, from Homeless to Dumbass teens and anything in between, as well as the demolition not being able to take place due to safety reasons, I mean would you want your workers, with all that big heavy and dangerous equipment, in a building with a ghost who has no quams about throwing that stuff around and killing workers?
Also what if simply demolishing the building doesn't get rid of the ghost either as it's bound to the land itself? That would be reason alone for a developer to pay to have a site exorcised before selling or redeveloping the property.
Maybe they want to redevelop the property and heard about the haunted events. They hire the team to get rid of the ghosts so they can redevelop the place into something else.
10$ for 2 dead friends
Why are the rewards so ridiculously low for going into deadly hazardous zones and putting your life on the line? Even if we assume everyone thinks your team are a bunch of weirdos who believe in ghosts, it still is effectively working for free compared to done labor, travel and the hazards involved. It can of course be explained by Gameplay and Story Segregation but your team's services seem to be wanted well enough to warrant better pay.
It could be that pay used to be higher and some people killed team members for the money. So the low payout is to make so killing your teammates just isn't worth it.
The money you earn in-game could just represent the fraction of your earnings that goes towards new equipment, as that is the only thing you can spend it on.
Does it actually occur to anyone that no company in the world has so much money to pay those who die like flies? That also begs the question where they get all that new equipment from, but let’s face it: ghosts are capable of killing large groups of people single-handedly. And it’s not far-fetched to think they have already…eliminated thousands if not tends of thousands of wee hunters. No company in the world would have so many funds to spend, even if backed up by government. Face it: you are expendable and treated as such. That’s not even capitalism, sheer utilitarianism.
You can think of it as disposable income. You need money to pay for your food, house rent and also the big ol warehouse you rent as HQ. Part of the pay probably goes towards those.
Voluntary ghost testing
In order to find out what kind of ghost the player is dealing with, a player needs to administer several tests to narrow the ghost types down. The thing that doesn't make sense to me is that some of these tests seem like it requires willing ghost participation in order to do, like the Spirit Box and Writing Book. If a ghost was attempting to avoid getting exorcised from their location, the simple solution would be to just not talk into the Spirit Box or not write in the book. Maybe the ghosts do want to get exorcised, and are participating so they can be put out of their misery? That would be a good explanation for any friendly or non-violent ghost, but what about the malevolent ones? They attack the teams, usually completely randomly, and it's weird behavior for ghosts that are also trying to seek help from the very same people.
Perhaps it could be the ghosts feel compelled to answer? This might be supported by how the ghost writing tools become increasingly ornate with each level.
