what use is it, really? you hatch enough, you'll run out of money and won't be able to hatch till you get more.
The only thing I can see is that when pets were first put in, the game devs tried to make it seem like pets were real creatures and you had to be nice to them and only breed them once in a while. Well if that's the case then they should be moms and dads (they don't have genders) and shouldn't be able to breed again as long as they have a baby. And they should grow and age to adult hood over time, not by playing games and eating snacks.
So since there's no storyline reason for the restriction on how often you can hatch, and there sure isn't a lack of system resources for it, please remove it.
I assume just as a way to get more crowns out of players potentially by having the system oh so slightly frustrating. Especially during double pet xp when more players are buying P9 and Energy Elixirs