I like whisky.
It's real simple. Tire pressure is what keeps the beads of the tire seated on the rims.
Less tire pressure equals less pressure against that wheel. Now space the rims of the wheels out another 2 inches from each other. The same amount of air will not hold that tire on a 10" wide wheel as well as a 8" wide wheel.
Also, How far the tire sticks out from the Jeep has more to do with backspacing than wheel width. Think of a stock Rubi wheel. Same width as my 15x8 wheels, but with less backspacing (numerically higher). That is why wheel spacers are used by Rubi owners that want to keep their cool wheels, and run a wide tire without rubbing.
I have run both 33x12.5 tires and now 35x12.5 tires on 15x8 wheels. I air down to 8psi most of the time and 5 psi on deep snow runs. Never had a problem.