Re: I wonder
A few ideas:
1) You'd like to insert yourself (or someone you know) into a famous movie scene for a laugh
2) There's a deceased person you'd like to re-animate without a very tedious cut & paste of individual frames from their previous works (dead actors)
3) You'd like to face swap a toy cat and real cat in a video without using snapchat filters
So, there'll be plenty of reasons that don't harm anyone and aren't pron related - it's just the majority of the effort has gone into various sexual fantasies. Doesn't mean we should try and ban it now.