I don't know, why do you say so? As far as I know, it just... happens.
What about losing sight of spoilers? The three biggest ones in Gurren Lagann, for example, are chronologically Kamina's death, the existence of the Anti-Spirals, and the size of the eponymous mecha. Yet I regularly see people spoiler the first one and leaving the second and third unmarked. Thanks to them, I spent the entire first half of the series thinking Lordgenome was the Anti-Spiral.
Well, that may be because the first spoiler is a character dying, and that's always considered a bigger spoiler than anything else. Still, you're right the other things count just as much too.
Aren't there also those who take this in the opposite extreme, and act like if a work isn't super-popular and known by pretty much everyone, they're sooooooo edgy and different for being a fan of something "obscure"? You know, the kind of person who will say something like "Oh, I'm watching this really cool show right now, but you wouldn't have heard of it because it's so obscure, and I'm one of the very few super-special fans who actually knows of it's existence!"
