1. No fun
2. Doesn't teach good decision making. JWs cannot choose the color of their underwear without first consulting watchtower publications. This stunts emotional development.
3. Discourages secular education. When young ones leave, they often missed out on opportunities to go to college. With no parental support, they are forced to begin working and cannot afford college immediately. This sets them back a few years.
4. Poor marital prospects/lack of understanding the opposite sex and relationships. Watchtower teaches that holding microphones, going in service and giving talks turns girls on. Flirting is evil. Thus young ones have no idea how to deal with the opposite sex. JWs have a fake public persona. Thus when they get married, they have no idea who they are marrying. Sexual repression also causes some to marry only for sex.
5. Complete abandonment if child doesn't choose watchtower. In modern society more and more young adults rely on the resources of their parents into their mid twenties. However, if you leave watchtower this support system dissolves.
6. Only acceptable prospects is bethel and pioneer service. JW youth are not encouraged to explore their interests or talents.