There is something about the "center" of a woman that is so fascinating to men. We dream about it yet rarely do we ever get a chance to see one let alone have fun down there. Oral sex is primarily about giving instead of receiving. We give oral because the receiver is the one who enjoys it the most, sometimes the giver likes it equally as well. A woman's muffin is soft and flexible to play with along with the fluids that are tasty. But all in all, think of the pleasure.
From a man's line-of-sight, seeing a naked woman body that close is truly a sight to behold. Her folds of flesh, her smooth shaven inner thighs, her tight belly and her breasts pointing upwards...ok, you get the idea. If cleaned, the vagina is also good to smell, almost nothing quite similar. Finally, when the man really knows what he's doing, watching a woman orgasm from lying down while "muffin munching" is heaven! Ya hear me?!? HEAVEN!
As one person pointed out, there are lots of men who "Won't Eat What You Can't Cook". Thus, you may want to consider yourself lucky to have such an open minded man. Sex is all about pleasure and intimacy, never has it been a bad thing. Enjoy your youth...just be careful
Generally oral is the easiest way to make a woman orgasm, and many guys love to hear their women getting off. It can be a real turn on to realize your woman is losing her mind over what you are doing.
It can also just be a fetish, like guys who love feet and get excited on sucking on toes. There is just something about it which hits their happy button. Hell I knew a girl who had an ex who liked her to masturbate him by rubbing her foot on his crotch.
Hell maybe he has a fetish about cute vag and also gets off on making you lose your mind. Nothing says it is a binary choice.
So enjoy the ride, and maybe find a few ways to further indulge yourself, say by telling him you want to ride the mustache or something where you have some control.
Hmm well for my opinion every some guys like to doit to pleasure there girl and well some girls may always wonder why does the he love doing it well of course to pleasure you amdbof course in my defence i have an ex that loved doing that and well in my case it would really get me goin so sometimes i let him sometimesi didn't and well its just oral sex but guys just some guys love to give the pleasure.