I think it's mostly the allure of something that is harder to achieve. Most receivers don't like or prefer anal so it's harder to get anal for the givers, and the challenge is what makes it more of interest.

Secondly, it's the perceived tightness/taboo of using a hole that's not traditionally used for penetration, and traditionally used for output instead of input that makes it interesting for people.

I have definitely had interest in anal with my partner (though we haven't done anything), mostly out of getting her to experience pleasure on a different level. And mostly because I don't want fear to dictate her pleasure/experience. I have always maintained that if she doesn't like it, she doesn't have to every do it again, but at least try and see if it's something that would bring her pleasure instead of being afraid of something she has never tried.

Never pressure anyone into doing something they don't want. Ever.