Actually they do. To the tune of ~$17,500 annually for a young person. That college diploma probably means its recipient will earn 50% more than without it.
For a guy like Nic Dowd, who is a Bio-medicine major with a 3.61 GPA, leaving his school without a diploma could be one of the worst decisions he could make. Fortunately, he's a senior and his college playing days are over. He should still be getting his degree when he's done with his classes this semester.
Remember that making the NHL as a prospect is not a sure thing. In fact, I would peg his chances as making it to the show as less than 50/50. There's a good possibility he ends up mired in AHL obscurity, riding busses around for three or four years before leaving hockey. Also remember that these prospects exist outside of hockeysfuture.com. They're real people who have to make a living, whether in hockey or not.
Most college hockey players don't decide to attend college only as preparation for an NHL career. They're there to get a degree too.
Nobody is asking where Scott Parse is these days. At least he was fortunate enough to make it to the NHL AND have that college degree now that he's not in hockey. I have no idea how many guys don't make it to the NHL, have no college degree, and spend their days in a crap job reliving the glory days in their minds or in beer leagues.