This community is weird (and horny)

Why most of TF2 sprays is PORNOGRAPHY??? I mean why even such type of sprays exist? I know the Rule#34 of the Internet but still I don't get why people use r34 pictures in silly game where Engies laugh at their sentries, POTIS, PAINIS and etc. Is this some sort of joke? Players that use r34 sprays please tell me why you do this?

Context: I am f2p 431+ hours for 3 years (sorry, I don't have much time to play) but figured out how to make visible sprays only a week ago.

Edit#1: HOLY SHIET 100 UPVOTES ALREADY? That's my first post.