I guess titty fucking is an exclusive guys' thing. I don't get any pleasure out of it, you see, and even though my tits are good for fucking, size-wise, I don't encourage guys to do this. From all my lovers, those into fucking my tits were just a small minority. For me, it's one way of second-party masturbation, like you get a handjob or blowjob from another person, just that it's the tits wrapped around your dick than a hand or lips. And just as there's no first-hand stimulation for me in any of those, there's none in a titfuck either.
For me personally, another drawback of titty sex is that unlike in a hand-/blowjob, I have no control regarding the guy's stimulation. That would make a turn-on for me, but since I can't even get this, I can only discourage guys from trying tit sex with me. But there are other things you can do to my puppies: You can pat them, squeeze them (careful!), lick, kiss, suck... you won't miss the tit fuck anyways.