There is one big problem. Each person who defects takes a risk, and if others do not defect, they end up losing. And the Washtowel will do all it can to make sure the ones that do not defect punish the ones that do to the maximum ability. They use labels such as "mentally diseased" to denigrade those who do defect, even with good cause.
Defecting this religion is much like moving to a foreign country (minus, of course, packing expenses and getting visas). You lose your whole "family" and what you thought were friends. Your whole lifestyle is likely to change, since you never got preparation to make it outside the cancer. Often, you have to get another job (not easy these days) and move to another home--people have been evicted, including children by their own parents, for defecting from the religion. You have to learn a whole new culture, one that you have been programmed to believe is rotten to the core. And most of the witlesses will not take that risk--including the risk that "one day soon", they are going to get destroyed if they remain out.