Another reason for no creeper eggs is that they can be used with skeles to make a very simple disc farm. I personally don't like this idea, just because of the people that would take advantage of it by getting tons of zombies and using it (effectively) as PvP. There's just so many ways this can be abused.
Thanks for that. I willalso add that you cannot respawn monsters back in wild and they can't kill you
Well even if they're not used in the wild, they would be used in town to make very easily accessible grinders, given you have a player with tons of eggs and a dispenser. Personally, I think that would take away the idea of actually going into the wild and risking dying to get exp.
I honestly don't even see any benefits from this based on how you describe it, just more unnecessary server lag. So it's a no-go in my opinion.
Another problem with this is if someone with a lot of rupees went mining (for example) and decided to eggify every hostile mob they came close to instead of fighting them. This would eliminate the survival aspect.