Speed limits exist for a reason. A moving ton of metal is dangerous, and the faster it moves, the more dangerous it gets. Kinetic energy is (mv^2)/2, so a little difference in speed makes a huge difference in a collision. Drive 40 instead of 30 and you've nearly doubled the energy of impact in case of a collision (x1.77).
I think most people actually acknowledge this, as very few people argue for raising or removing the limits. Yet, most feel OK speeding, probably because they each individually think they drive better than the others.
I'm not sure repression is the solution, but there's clearly a problem with speed. And for that matter, I'm pretty sure that other traffic laws also belong to the list of the most commonly broken, partly for the reasons above, and more generally because people don't always understand why they exist.