Full Answer
Just because you have an anime picture on your profile, doesn't make you stupid or your opinion doesn't matter. Every opinion matters, whether you have an anime or video game character as your profile picture. In a discussion or debate, the value should've been lies on what you say, not the freakin profile picture.
There are two main reasons why, either because they love the character they put as their profile picture, in other words, it's their waifu or husbando, or because the anime character they chose as their profile picture matches with their personality, or matching with a personality they wish they have.
0:164:43What your profile picture says about you! (1M Sub Special) - YouTubeYouTubeStart of suggested clipEnd of suggested clipPeople a hair you like annoying people anime boy you're a girl anime girl you're a boy filteredMorePeople a hair you like annoying people anime boy you're a girl anime girl you're a boy filtered anime character.
PFP is an acronym in texting and social media. It means both picture for proof and profile pic.