What
>>28168141 said.
It probably happens, everyone knows it happens, but no one really talks about it.
Might explain why 90% of the population is single, and why there are so many single moms. People probably only hook up for the sheer sake of procreation before the dude hurries off on another 'pokemon adventure'. What, you expect your man to be gone for weeks, months, years at a time, and he isn't putting his dick in SOMETHING? Same can be said for all the moms left at home by themselves. Yea, Mr Mine is Ash's new step dad. Some kind on an adventure with there Pokemon is going to learn about sexuallity at one point or another.
Does it happen? 100% yes. Is it socially acceptable? It's probably an understood taboo, but again, one of those don't ask don't Tell things.