It could also be a selection effect -- if you're doing something even though you're not supposed to, it must be something you really like.

Or an evolutionary nudge in the direction of hypocrisy.

More precisely, if the tribe has bothered to prohibit it, it must be something that advantages you at someone else's (possibly the group's) expense, and therefore you should be:

a) Encouraged to do it more, while...

b) Exhibiting plausible self-punishment when caught, to maintain group ties.

The former explains the increased reward, the latter the social behavior aspect.