A quick introduction. I've been married for about 25 years to a wonderful wife. About 10 years ago we started fooling around with butt plugs, and my wife discovered she loved them! So one thing led to another and soon we'd done anal sex, and there was no turning back. My wife is quite a bit smaller than I am, and one thing that was always bad about vaginal intercourse is that when I would thrust in all the way, I could hit her cervix and that was no fun! So vaginal intercourse for me meant shallow strokes, and avoiding certain positions where I might go too deep (like missionary with her legs far back). With anal I discovered I could thrust as deep as I wanted without hurting her, and was that an epiphany! As all of you guys on here know, there is nothing better than ejaculating into a tight ass. The rectum is essentially bottomless and so for the first time I could fuck her with my entire cock. And instead of ejaculating with my cock pressed up against her pussy wall, I learned how much better it feels to release into the deep cavity of her rectum.
All that said, we aren't anal only. My wife enjoys some vaginal sex as a warm-up to anal. I'm fine with that since I know the good stuff is coming, and maybe fucking her pussy serves to remind me how much better it feels to be in her ass.

Who knows, maybe someday we'll be anal only. I haven't broached the subject with her yet. I have told her how much better anal feels for me and that I intend to come in her ass every time. So maybe someday.