Goldekint – “Another issue is abuse. children who have been abused often leave the fold if the abuser was/is frum and wasn’t ostracised. who knows what these kids went through or still go through. sometimes it’s parents or close relatives who are the abusers.”
Your last line -is this an oversight or you didn’t mention them on purpose? A good portion of the time the kids are abused by Mechanchim or teachers!