Holly of The Pervocracy says

There’s no masturbation for kissing. Kissing your hand just makes you feel like a dork. There’s no good kissing in porn and there’s no kiss fetish community. Kissing on screen, even the kind of kiss that shoots straight to your groin and makes you gasp and clutch the back of your partner’s head, is G rated.

The rest of her thoughts about kissing are cool too. Read about them here.

All excellent points, of course. And while even “mainstream” movies don’t necessarily capture the intimate majesty of real kissing, but considering the ways they tend to botch cunnilingus or intercourse in porn it’s probably better all around that pornographers don’t bother trying. :-)