Basically, next time you're on a group ride, if you're sitting 2nd in the pace line, try accelerating out from behind the lead rider to hit the front and see what happens to your speed. The guy in 2nd has the advantage every time.
It's exaggerated in a bike race because the cyclist has enough speed for drafting to make a significant difference (unlike the marathon runner) and the road is wide enough that a cyclist can't maintain a legitimate racing line and still block someone coming around him on a sprint (as happens in close f1 finishes).