I'd surmise it's because several states (CA comes to the top of mind) set speeds in excess of 80 as a potential felony enhancement.
iirc in CA it's 20mph over the speed limit, or speeds over 80.
The insurance companies probably want to know who to raise rates on.
Which is crazy because when I do 80 in Mostly PA and NJ I am getting passed constantly.
I just looked and both PA and NJ, have way below natl average car accident deaths per 100K drivers, even if death in over speeding seems to be a a significant contributing factor to overall rates.
Interesting to me. I wonder what are they doing right.