The anus is an erogenous zone. There are tons of nerve endings there, and if you touch it right, whether that’s with fingers, a tongue, a penis, or a toy, it has the chance to feel really, really good. I like anal sex. I haven’t done it much in the last couple of years because of other medical things, but it can be really enjoyable. It also presents the opportunity for double penetration, or sex with a plug or toy in. It’s a different sensation.
I understand why you are not super into it, but I will say that there’s a huge difference between doing it right and doing it in a way that will cause pain and trauma. If you ever get curious again, maybe try starting with playfulness that has no expectation of penetration to remove that from the table and relax things.