JWs and other high control groups attract the 'weak', the 'gullible', and the 'lazy'. This does not mean that all of those terms apply to all JWs. But usually, at least one does. It also does not mean such people are inherently or permanently 'weak', 'gullible' or 'lazy'. Unfortunately, being born in to such groups tends to produce people who are weak, gullible and/or lazy.
The 'weak' lack the confidence to leave even if they may suspect problems with the organisation and its teachings. They are generally either born in, or become a member during some period of hardship. Depending on individual circumstances, such as not having any family outside - maybe not knowing anyone at all outside the organisation - even people who are relatively confident may still fall into this 'weak' category, because the difficulty in leaving is usually considerable. If they develop sufficient confidence to leave, they are the least likely to join another religion on the 'rebound'. If they are otherwise 'disfellowshipped' for some 'sin' (other than 'apostacy') they may try to return if an alternative social network cannot be established.
The 'lazy' find it easy to be involved with high control groups because they don't need to think for themselves. Many 'lazy' JWs are only intellectually lazy. They may be born in, or may join the organisation because their lives lack 'purpose', or because they are lonely and the congregation provides an 'instant social circle'. They tend to 'coast' in 'the truth', but may make 'advancement' as a 'ministerial servant', an 'elder' or higher if 'encouraged', particularly if it is the path of least resistance. If they do decide to leave but still lack motivation, they will probably seek out another group that provides a guiding framework, but dissatisfaction with JWs may cause them to seek out a more mainstream belief system. If they are disfellowshipped, they may try to return, but will probably become involved with another group instead.
The happiest of JWs generally fall into the 'gullible' category. They are usually born in, and others join as a result of extended contact with a JW schoolfriend or colleague. They genuinely believe they have 'the truth', and are extremely resistant to information not sanctioned by the organisation. Many in this category will never think of leaving. They are most prone to superstition, particularly in relation to a 'hope for the dead'. If problems about a particular incident or doctrine do get through, it may be 'a long way to fall', which may result in significant depression or unpredictable behaviour. If they do leave for doctrinal reasons but do not break free from the 'gullible' persona, they are the most likely category to seek out another ultimate 'truth' on the 'rebound', and some may even start their own group. If they are 'disfellowshipped' for some other 'sin' they are the most likely category to try to return.