I'd say there's an under abundance of kissing because there's an over abundance of rape. (And way too much bonding/comedy rape/forced to marry fic. Shudder).

I love the kissing - but as to writing it, that depends on the pairing. I don't see Snape/Sirius having long, sweet, affectionate make out sessions.

Hagrid, on the other hand, would be a face eater.