Without getting into the Freud of it all, it is taboo and these are games that let you seek out new things that would otherwise be thought of as "off-limits". It's the sexual equivalent of daydreaming.
It's too big if I run out of names to give the girls in the game. I am not going to randomly choose "Diane" for a character because I don't know one. I like using names I know so I can associate the game...thats my take
A little lactation is fine but don't build the entire game around it...I would say that about any "fetish" though. Sprinkle it in don't shower us in it! Hahahha
Sure, if the game is more complex and has a system built in that makes the grind too tough or the decisions don't come easy for a great outcome, why not? More is better