I am sure there are a lot of JWs in their 30s - 50s who are only still there for the sake of parents.
Very true, however, I am sure there are a lot of JW's in their 70's to 80's who are only in still for the sake of their children and ultimately themselves. Nobody wants to be old and infirm without the support of their family. Too late to leave, insufficient advantages compared to the status quo.
George