The same that puts kids on starships facing destruction every other week...
To be fair, if the alternative is leaving your kids elsewhere for months or years at a time (especially if you go by TNG's original premise), I can't blame parents for wanting to bring their kids with them.
Besides, it's not as though planets in Trek are necessarily any safer. At least a starship can get out of the way of danger when it's not busy putting itself in the way of danger.