The reason measurables are so important is it shows how well a player will translate their game to the NFL. A linebacker who is a little taller and has slightly longer arms is probably going to be able to add a little more bulk to his frame, create better separation from potential blockers, make interceptions/ passed defenses easier, and make tackles easier. Broad jump shows first step explosion when rushing the passer, cone drill change of direction etc. When .05 of second is the difference between tipping a pass or not, or getting a hand on the quarter back before he hrows it than it's pretty obvious a .2 seconds difference on a 40 or 6" on a broad jump is extremely important. The people who down play measurables usually point to a few exceptions to the rule. However, if you look at two guys who both had great production in college and have almost the same height and weight, than the guy with greater combine numbers is going to have the potential to be a better NFL player almost 100% of the time (obviously injuries and character issues aside). The comparisons to discredit combine results are usually comparing a guy who didn't produce much in college and had a great combine to a guy who produced a ton in college and had a slightly worse combine.
