For me it's instinctive to watch a woman's mouth and tongue go to work on my shaft and immediately want to rise up and have that mouth and tongue go to work on my mouth/tongue..it's just natural.
Only turn off is kissing waaaaay after nice little session when her lips are dry with no more gloss or lipstick from all that earlier sucking and spit flying.
Well, I darned sure am not gay, but this is something my late wife introduced me to years ago, and I feel fortunate to have a ATF who is willing to carry on the tradition.
Depends on the reason you want to kiss her after she blows you. If its because you're turned on and love her sexy mouth, I don't think anyone'd begrudged you some DFK. But, if its because you like the subtle hint of your own cock and dick-butter on her breath, then you might be gay.