It's because porn is NOT run as business. Despite the humungous amounts of money spent on wank-fodder it's still largely the province of hobbiest, malcontents and jaded, hedonistic, self-destructive types.

They want to be outlaws! But they also want to be left alone to do whatever they want. So when they ARE left alone they don't feel "outlaw" enough and push the envelope a bit more to get a reaction!

That distant thump, thump, thump you can hear ISN'T legions of girls getting slapped or donkey-punched, it's the inevitable jackboots of the backlash from the forces of law and order which will march into the porno biz and kick everyone in their collective nuts.