Dark Autistic, you need to get out more.

Buttholes are very widely thought of in sexual ways in some cultures and subcultures. Sometimes it is because single people wish to be sexually active while retaining their "virginity" for marriage. Sometimes it is because using the tradesman's entrance is a very effective form of contraception. And there are many other reasons which I won't go into.

I think the big difference is that an aspie is more likely to mention their butthole interests in the wrong company.