Families were probably placed onboard the Enterprise and other ships because of some politician who wanted to shift StarFleet's budget away from space exploration to defense. Think about it.
"1,014 men, women, and children were killed earlier today when the Enterprise-D was destroyed by some strange inverted nebula that caused the crew to turn inside-out. Horrible deaths, but the worst thing is that this never had to happen. First we create an enemy out of the Borg that threatens our very existance and now this. How many more lives will be lost before StarFleet stops poking its nose where it doesn't belong?" -- FOX News, Stardate 47457.1.