Since kollel life became “the thing to do”, there have also been many more people going off the derech. Someone once told me they’re directly related. In Judaism, it’s always been said that the mother sets the tone in the home as far as yiddishkeit goes. It’s a big part of her job to make the children love Judaism, and instill the proper values in them.
Since in kollel families, the mothers are usually out working, and someone else is taking care of their kids, the mothers don’t have as much opportunity to instill the proper values in their kids. This can cause kids to go off the derech.