Your anus is vey sensitive, and in a deep and profound way. Not only that, but your anus is rarely touched by the outside world so being licked is quite a shock for the ofres several times. I don't care for it myself, but I had a number of GFs in college that I introduced to rimming, and each of them loved it. One friend of mine had been attached as a teenager and been forced to have anal sex with her attacker. She didn't want her butt licked because she was afraid of the contact, and her memory of being attacked was profoundly disutrbing to her. After coms conversation about it, and allowig me to try it once, she was hooked! She said it was "healing", "soothing", and downright "therapeutic". It also made her pussy wet and sloppy. That's always good.
Good luck with that.