Truth is that different driving styles (using the same car) will want slightly different air pressures. Different (aftermarket) tires change the desired a pressures, heck even aging of tires can desired air pressure upwards or dwonwards.
Secondly, once the optimal air pressure is found that maximizes traction, there is a significantly wide pressure interval surrounding this optimal point; that 2PSI down from optimal might give one driver a better ride he desires, while 2 PSI up from optimal might give another driver the steering response he desires.
There is not one pressure that can satisfy all drivers and their preferences--let alone the miriad of changes drivers can do to cars {after market wheels and different tire sizes, brake pads, springs and shock changes, ride hehight adjustments, suspension aligments,...}. So use the tire pressure indicator in the door jamb as a starting point guess, and work you way up and down until you like the way the car feels.
However, there is a little device that can tell 'any' driver if his tires are operating at the correct pressures for 'him'. This device is called a probe tipped pyrometer. It is easy to use, and only requires a few seoncds of time after a long drive in order to ascertain if the tires, pressures, alignments,... are proper for that driver, on that drive in those temperatures and condistions.