Interesting thread. It is pretty cut and dried from my perspective. 750 players in the entire world will play MLB at any moment in time. There were around 7.129 Billion people in the world in 2013. So, to answer PGStaff's thread question I look at it the odds as not particulary good. Yes the same can be said for other professions. But other professions don't have a limited shelf life or timetable that a professional athlete faces. Very few have the freakish skill set, discipline, will, and unbelievable luck that it takes to be a professional baseball player.
With that said, I think there comes a time where every player has to ask themselves if baseball is giving or taking away from their lives and goals. When it is giving back such as a baseball scholarship or an opportunity to attend a university that a student wouldn't usually have access to....that is a positive. When it is taking away from something else the person could be doing for himself or family then it is time to be doing something else.
Over the years, my personal observation is that many players overestimate their talent and underestimate the rest of the (world) field. I've seen it in high school and college baseball. In 1984 I tried my hand (very briefly) at professional tennis. Let's just say it was an eye opening experience for a young man who learned quickly how many unbelievable tennis players there are in the world. I'll assume it happens at the MiLB professional level too, because the feedback I've gotten from some MiLB players is people still try to get by on talent alone. In baseball, you have to have the talent & desire but you also have to have any unbelievable amount of luck. Do you want to bet your career on luck? Some do and some don't. At least 750 decided the risk was worth the reward.