Here's an even more sobering point...

Many of those players will keep training and hoping to make it in the NFL. This will continue for several years for some of them. In the end, they will have wasted years when they could have gotten a start in a career. This pattern plays out even more in basketball, which has various semi-pro leagues around the world. Lots of young men waste many of the best years of their lives chasing a dream that will always remain out of reach. I have seen it happen to a few people that I have known well.