They actually do!
http://www.nfl.com/news/story/0ap30...eboots-veterans-combine-as-pro-player-combine
I really like the three cone at certain positions for one reason: it's shown itself to be predictive. I really pay attention to it at EDGE. I get why some people think it's silly to put stock in guys in shorts running around cones. At one time I did as well. But when you look at the high end times over the last 10 years or so and what those players went on to do, it's tough to ignore the correlation.
I think that where people go wrong most of the time with combine numbers is knowing what numbers have shown themselves as important and at what positions. Three cone and broad jump are pretty important for edge rushers. Forty time not so much. Forties (at least minimums) matter for corners, but I could care less about their bench. I'll take a back who kills the jumps and agility drills over one that runs really fast. Things like that.
But the most important thing, I think, is to find where the tape overlaps with the numbers. A guy like Bowser is an elite athlete. And while he isn't the most refined player on tape, he shows you some things that are impressive. He was regarded as a 2nd round talent before the combine ever happened. Put those things together and that's a guy I covet. There are guys every so often who kill the drills (e.g. James Cowser or Tyler Starr) but aren't good enough on tape to get drafted. It's not like they go on to be good just because of that one test.