When you're kissing, there's nowhere to hide. In fact, kissing can be an intimacy gauge. Kissing a partner we don't like, especially an enthusiastic one, can be an awful experience. Then there's the issue of style. It's as if one of you is doing the mambo while the other waltzes.
Some people prefer subtle and gradual the stealth tongue approach.
Others are more direct and even overpowering the invading army approach. Neither approach is wrong, but each can be unpleasant to someone who wants something different. Breath also plays a big role in couples' kissing compatibility. If she doesn't like the way he smells or vice versa, kissing can quickly disappear from the repertoire. In fact, since kissing puts us so close to another person, things like dirty hair, scratchy beard, nose hairs and scented makeup can all become key issues in reducing the desire to kiss.