Going back to what highrev said, every tire has an optimal range of temperature and pressures they should operate under. Stick a driver who knows what he's doing in a car with pressure that's on the low side and he's more than likely to rip it right off the rim
You won't get tire temps unless the tire deforms. Most of the time, this means putting a lot of load on the tire. With someone that will never put a lot of load on the tire, lower pressures mean the tire will deform adequately with a moderate amount of load. Stick a real race driver on too low of pressures, though, and he'll be liable to destroy the tire by overloading the tires. Tire pressure is a huge factor in how much load a tire can carry.