When/how/why max tire pressures raised from 35 PSI to 44 PSI?

If you read the tire a load range E will say 3520 LBS @ 80 PSI, This doesn't mean 80 PSI if you have 1500 LBS on the tire. My old M/T say 20 PSI MAX at 1430 PSI. If I ran 20 PSI all the time the tires wear out in the middle because there is too much air pressure. The street rod weighed 2200 lbs total, that would be about 900 lbs on the rear total. You need to go by the tire wear and the weight not by what MAX is on the tire.