Bob starts with no equipment whatsoever, not even armor! Hell! Everything he has at the start of the story is his Goofy Print Underwear! ...And the king still thinks he's over-equipped!
Downplayed: Bob's given what was left in the armory. His quest is important, but the war against Evulz has drained the supply. The sword's rusty but was well kept when it was owned perviously, and the shield is actually pretty good.
Emperor Evulz stole most king's and Bob's equipment, leaving them with the weakest one.
Bob is a private citizen who set of on his own without proper gear.
The king who sent Bob was Genre Savvy and knew that he would be fine without the best equipment.
Bob is questing for a legendary sword, a shield that can block anything, and armor that has amazing effects on it's wearer, as either part of or the whole quest, so it might just seem prudent to give Bob enough that he can protect himself against known monster around the village/city he is leaving from, possibly thinking that he will get at least one of the set before he gets into truly deadly areas or just doesn't know that next village over they have a more deadly monster problem.
Bob and the King have no idea what they're sending bob to. Bob might have the sharpest sword in the kingdom and the best protection, but where he's going that counts for very little, possibly the best weapons are made out of pure magic rather than materiel, meaning that Bob did have good equipment, but the situation made it either worthless in comparison or his weapon just isn't as useful.
Bob is the latest in a long line of would-be heroes who have claimed they could defeat Emperor Evulz, and all of the previous ones have been defeated and subverted. The King is holding back on the goodies because he doesn't want to risk having such valuable equipment falling into enemy hands and wants to be sure Bob is actually the Chosen One before he trusts him with anything beyond easily replaceable standard-issue gear.
Bob majorly screwed up and the King is trying to let him redeem himself in the course of his quest.
Bob is airdropped deep behind enemy lines with a stealth glider to avoid being shot down before arriving at the place where he must be dropped, and he can only carry limited equipment. Sure, a BFG would be great, but given the rate at which such babies eat through ammo, it's not gonna be useful to him for long, so he's forced to bring with him only low powered but reliable equipment and make do with what he will find.
Before he can begin his quest, Bob must turn in all his equipment and cash and get them replaced with a standard issue knife and shield.
Zig Zagged: Bob begins his quest with a knife and a shield but there is a shop nearby that sells a sword said to be incredibly powerful. The sword costs 100000 gold, but Bob find that much money after he kills the a very weak slime nearby. When he buys the sword it is almost as weak as the knife.
Bob begins his quest with the best equipment he or his king could afford.
Bob starts off with endgame weapon and gear because he's playing on New Game+ Mode.
Enforced: "We don't want Bob to plummet through weak enemies that easily. Do we?"
Exploited: Drill Sergeant Carl gives his new recruits a mission to take on a gruelling exercise with only a small knife and several changes of underwear... because he wants them to improvise and think for themselves instead of relying on equipment they might not always have.
Defied: "I will not go until you give me something better!"
Discussed: "Are you sure sending Bob with a knife, a pistol and C-4 is going to be enough?" "Unless you have a plan to insert him deep behind enemy lines with a lot of equipment and without him getting shot down, we're gonna have to hope it will be."
Conversed: "Don't you find it ridicoulous for heroes famed worldwide to go on a quest to kill Cthulhuwith a sword?
Implied: It's never shown in the inventory, but after a few points, the sword and shield Bob are using is changed and he gets a stat boost when this happens. By the end of the game, if one goes out of their way to not gain stats, they see the starting and middle boosts are vastly improved.
Deconstructed: Bob's starting weaponry is woefully inadequate to take out just about any opponent, and he ends up stuck on the receiving end of a Curb-Stomp Battle very early on.
Bob's starting weaponry is woefully inadequate to take out just about any opponent, so he doesn't.
Bob's starting weaponry is woefully inadequate to take out just about any opponent, but he is so good he manage to do it anyway.
Plotted A Good Waste: The kingdom bob comes from is one of the few that remained unattacked. To prevent an attack the good king sends Bob with the best weapons he can part with. As you adventure farther and father, you find out just why your starting weapons can easily be replaced by better ones: The kingdom is actually poor and has few things going for it aside from farming, and the reason they weren't attacked wasn't because they could defend themselves, it was because they just weren't worth it.
Played For Laughs: When passing by a lake, Bob fishes for a bit and catches one, entering a random battle with it equipped he will say "Wow, this is better than that junk the king gave me. Why don't the guards just use fish?"
Played For Drama: The equipment shows what the king thinks of Bob, while one with less skill gets weapons that are much better than the poor items than Bob got, he considers multiple times betraying everybody and simply joining Evulz because of how clear they are making it that they want him to die on this quest.