IMO it is likely the MO people probably do leave more than Charedim, but I dont think it has anything to do with hashkafa.
It IS easier to leave if you are MO than Charedi, You likely speak english better , You likely dont have a jewish accent, you likely dress like everyone else, you likely have a secular education , you likely can behave in the outside world and most likely your family will not disown you.
If you are Charedi the break is much more extreme, and more difficult to do. Also they are married younger and breaking away involves kids and people cannot function in regular society.
If you want to say the keeping people in almost by force works better and keeps more in , you would be correct, but I am not sure if having miserable members is such a good idea either.