Married couple here, long-time anal only but new to realising this is a thing for people and there's a whole lifestyle around it!
Ours is a D/S dynamic, mostly around orgasm denial for her. Started after our 2nd child was born and vaginal sex was painful for a while so anal became more of a regular thing. The dynamic shifted more to D/S and she had some behavioural issues that I started dealing with through spanking and orgasm denial. Rough going at first, particularly since she finds it really hard to orgasm without direct clitoral stimulation.
Now there's a lot of edging for weeks usually and I let her cum as a treat. A lot of begging as I go down on her almost to the point of no return, then bend her over for a great anal session, holding her hands behind her back so she isn't tempted to rub herself off. I usually finish in her or with ATM, and afterwards she's very affectionate and attentive. Sounds weird when you write it out but it works for us, both really happy and the marriage is in the best shape it's been since the honeymoon.
She doesn't really desire vaginal penetration anymore, but can't let go of her desire for clitoral stimulation. As I keep telling her, "you don't NEED it, you WANT it".

Anyway great to be here and learn that we're not solo freaks!