Because he's selfish, plain and simple.
You're dating the dude whose sole purpose is get his rocks off. Has he always been like this or is this a more recent problem? Some guys are all about the ladies and their desires early on and then start to get lazy and less concerned with their woman's climax as times goes on.
This is a problem, but probably a common one. And it goes both ways. As couples grow they are less concerned with all of the fun of foreplay and start having sex two times a month on scheduled timeslots. Hopefully this isn't you and yours.
The good thing is that he might not realize he's being selfish or that he's just not engaging in foreplay. Hell, he simply might not be thinking about it at all. Communication is the key here.
Which means, you should bring it up to him. I mean, closed mouths don't get fed. Hmm, that's an interesting cliche here considering how his mouth is closed but I'm pretty sure he's still getting fed, proverbially, since he's still getting some of that stank from you.
That? Was dumb.
Anyway, the only way to fix this problem is to tell him that he needs to engage in a little more "romancing of your stone". Or better yet, let him know how much it would mean for you and how it would make you feel closer, etc. You know, all that buttery fluffy stuff women say to make us men pretend we're mushy on the inside.
If he's like, "naw, I'm good," then you know what you're dealing with and can then decide how you feel about residing in a foreplayless relationship. If you can live with it (which I'm guessing you can't since you wrote in), then great. If not, then you'll need to get your needs met elsewhere or by other means.
It was written.
spell check fool
spell check deez.
lmfaoo classic response panama