They will cannabalize the bebe's if you don't seperate them. I am guessing the story goes this: They fight hard food already, So they have floater eggs to increase the chances of the dragonets spreading (vs. increasing in one spot and decreasing food supply) and if current doesn't send the eggs away....well, the parents get an extra meal.

This is entirely my theory. Hopefully other MAASTards will pipe in their own knowledge and food for thought.