See, this is the problem. You either risk getting a ticket by keeping up with the 15mph+ people in the left, or you deal with grandma and grandpa doing 10mph under on the right. So a lot of us end up having to leapfrog back and forth. I just want to maintain my socially and legally acceptable 4mph over.
But they do. The assholes who want to go fast will weave in and out of traffic which increases the chances they lose control. Blocking traffic won't suddenly make these people good drivers, it makes them irritable and impatient and more likely to pull even riskier manoeuvres.
Seriously, I can personally attest to seeing people doing batshit crazy things such as passing on the left, off the road, on uneven grass, with one of those decapitate-ey looking cable barriers within 2ft of their vehicle, all over traffic going 55MPH in a 55MPH zone.
If the entire left lane is rolling out at 15 over, cops aren't going to pull over everyone. They'll get you though if there isn't much traffic and you're by yourself out there getting it.