There's a lot of difference between being ripped apart by a werewolf, being killed viciously by someone in a fit of righteousness, receiving the Dementor's Kiss or whatever horrible way can be thought up for Snape's death and falling whole and (supposedly) healthy through some drapery. :D

But take heart, this is the magical world. Snape can always turn the afterlife upside-down or be remembered in MWPP era fics... or, of course, he has invented a potion to 'bring him back'...