It's bad for most kids and bad for the league.
Yes, kids want their 2nd contract but many of these kids are not ready and will not make it. It's a numbers game. The NFL has x amount of roster spots and y number of players.....if you are not prepared to compete mentally or physically, you will not make it. That's what some of these young guys will find out. So eventhough they think they are doing themelves a favor, staying another year would probably help them bridge that trasitional gap by becoming stronger, tougher mentally and more experienced. Oh, and if they actually care about life after foobtball, since most kids don't make it in the pros for more than a couple years, they could actually get a free degree and find a different way out of the rough neighborhoods.
However.....if you are a running back that carries the ball a lot in college, go and do not look back. The body can only take so many tackles and your clock is ticking. That is why i DO NOT understand why all these young RBs want early playing time and go to schools strictly on depth charts. Why play as a true frosh and beat up your body? You can't go pro for 3 years. Sit back, learn, be a part time player and explode for 1-2 years and leave. That way you get to the league fresh.