Can the combine really make or break you?

With the NFL's combine coming up quickly, it is time to start looking at how it can effect ones draft status. Everyone clams that 40yrd dash is worth millions of dollars, but on average how many plays actually travel 40 yards. The average is around 3 plays a game where a play is busted lose and travels over 40. So why is there so much pressure on the dash? One may think that it is used, because at worst you will draft a guy that can run down in 4.3 seconds and cover kicks, granted there is still the chance they will miss the tackle.
With the NFL being the most physical sport in the world, one would think there would be more contact drills at the draft, but in all actuallity there are none. The draft is all about speed and what you can do with or without the ball when you have no fear of contact.
I personally believer that there should be way less pressure on the draft, because of such people like Hayward-Bay of last year. His combine was so impressive, he jumped from the second round all the way to a top 5 pick. Only to have a season of dropped balls and missed blocks.