I don’t get it! Need some insight

I really enjoy sex with my boyfriend, we’ve been together for over 8 years now, will be married December; he’s attentive and mindful of me. He makes sure on his end that sex is enjoyable to me. We communicate really well about the things we want and don’t and make a point to add some spice to our love life. One thing I just don’t get, he is obsessed with going down on me, I told him a million times….. I don’t want you to feel like you have to do that….. I guess to me it seems like, why would you wnat to do that if you don’t have to lol …. Im really sensitive, not always in a bad way but feel like there’s no way he would would be that into it. Apparently I’m wrong 😆 I’ve asked him, “is it a thing, like what do you get out of it?” his response is just, “ I want to pease you and make you feel good…..”but you already do in different ways, the regular sex is amazing. Listen im not complaining…. I just don’t get, I understand some guys are into boobs and others into booties, I have no boobs but I have an ass, I get that he loves a heavy bottom but, voluntarily eatin pussy. I feel like you can’t seriously like that all up in your mouth, I let him do it because he says he wants, but like y… oh and same thing he’s started licking my ass, like what the heck. Idk I need some insight, this boy is something else sometimes im into it other times I don’t care for it.

Side note:

I’ve read some of the comments. This is not a situation where he doesn’t understand or has passed any boundaries with me, like I said we communicate, if I don’t want it then he won’t/wouldn’t. If that’s his jam I also want him to enjoy what he wants. I was just saying, I just don’t get that desire or attraction. 🤷🏽‍♀️ thought maybe someone would say oh so guys are into that because xxxx or idk someone ask their dudes and get me their reasoning. Sending 💕 thanks for entertaining my post.