The NFL Scouting Combine is a great showcase for some well-trained athletes, but it's also more than that: It represents a chance for football prospects to prove they have what it takes to make it in the pros.
That's especially true for guys who are perceived, for one reason or another, as questionable investments. They get a shot to show anyone who is interested that they can catch the football more consistently than their reputation says, or that they do have the technical skills to excel at the quarterback position. This often goes beyond pride; if a prospect can lift himself up a round or two -- or a spot or two in the first round -- he stands to gain a significant amount of money.
Of course, a good combine performance can't make up for a history of poor play in college. People don't care if you're a so-called "workout wonder." They want to see what you are as a football player. A guy who works out really well in Indy but grades poorly as a competitor won't improve his stock much. However, a guy who grades well and wows scouts can turbocharge his value.