I think some people get on this train and they don't really know where to get off or what to do whenever they do get off. So inertia keeps them riding along, doing something that is comfortable (even if they don't enjoy it) to postpone figuring out what to do next. Eventually the train gets to the end of the line and they have to get off and figure something out.

I think this is part of the tragedy of our parents generation pushing college at all costs. It is very hard to know what you want to do for the rest of your life as an 18 yo. Even worse to take on all the debt in the world for something you don't end up loving or without a good path to repayment. In previous generations, some of these people would have done a stint in the service or taken a gap year but now there is too much pressure to know "now".