[overlander63]

Tire pressure recommendations are based on many factors. Vehicle manufacturers will specify a lower pressure than max for the tire to compensate for defficiencies in the vehicle's suspension, or unusual wear patterns that would result from using maximum inflation.
The higher the tire pressure, the less rolling resistance, the less sway from sidewall flexing, and less heat generated from sidewall flexing. On the other side of the coin, running maximum pressure on a lightly loaded vehicle can cause a harsh ride, bruising of the center of the tread, and excessive wear in the center of the tread.
Underinflation can cause excessive sway, excessive heat generation due to sidewall flexing, sidewall failure due to the heat, and tire wear on the outer edges of the tread and, in extreme underinflation cases, wear on the sidewall.
My truck manufacturer recommends 51psi front, 80 rear, I run 55 all the way around based on loading. My trailer is supposed to have 50 psi with load range C tires, I have D rated tires, and run 60, instead of the maximum of 65.