Once when my sister and I were teenagers, she was hogging the computer and so I just picked up the chair with her in it to move her out of my way. As I walked past, her friend (whom I hadn't touched) used her bite to make an attack of opportunity against me. It wasn't gentle - there was no blood but there were tooth-marks.

I had mixed feelings afterwards. On the one hand, it hurt. On the other hand, a girl touched me. With her mouth. I had never been kissed at that point but being bitten was close...

(I didn't end up marrying her.)

Also a d6 bite is nonsense. The average commoner has 4 hp and 10 strength, so one commoner would be able to kill another commoner with a single bite 50% of the time. I'm not saying a human bite can't be lethal, but it's not "stabbed with a shortsword" lethal. Meanwhile, even a d4 bite from a level 1, 16-str barbarian is already invariably lethal to a commoner.

(Yeah, I know, HP isn't supposed to be realistic, etc. I just hate fun.)