1) That depends on the creator, LAGS' wish
2) There's already an egg laying system in the game.
If you are talking about giving birth to baby goblins, baby skeletons, baby snowmen and etc, then this game will get more complicated, bugs will be harder to fix, and thus will take more time to release. This programming phenomenon is called "feature creep"
Furthermore, what do you do with monster babies after giving birth? Selling them? Eating them? Or just let them be? That's morally messed up, even for a hgame 😰
Not to mention, there's already a pregnancy (egg laying) turn on/off switch in the options.