Trucking Companies Goverened speed

Thanks for all the answers. Reason i was wondering was I got a couple of driver friends that are always telling me how their slow trucks are burning them out. My friend at Crete says his International Pro Star goes 60mph. I used to be at CFI which is now Conway Truckload, and they used to go 70mph now they are set at 65. I dont know why they lower speeds.... Ive heard the reasons being fuel economy, safety , wear and tear , insurance etc. It makes for quite a debate. But one thing i feel it does make the job more stressful. Alot of drivers i know dont care about how fast their Truck runs, then again i know drivers who vow to never be in a slow Truck again. Im with the latter. I currently dive a 2009 Kw W900 with a 18 speed and 3:25 rear ends with a Acert Cat C15 set a 475 hp with the DPF. I usually set the cruise at 72 mph in fast states and no more than 5 mph everywhere else (especially cali), and i haul reefer loads coast to coast usually over 40,000lbs and right now my Truck is getting 6.35 mpg. Thats not great fuel milage but my friend has a automatic Volvo at Interstate that goes 62mph and he says he barely gets over 6.0 mpg . Makes no sense, and we idle about the same . Anyway Im sure there are more factors to consider ( not letting a rookie have a wide open truck) but It seems to me pretty soon EVERYBODY will be cut back to 63mph while we cruise down the highway in our spaceship looking big trucks with our EOBRs and Digital logs and weird trailer fairings and disc wheel covers and flyswatter mudflaps and no Idle laws...Wait a second thats already happened! I guess i will be assimilated soon...