The only reason they use nitrogen for pressure stability is that the fill lacks humidity. It has nothing to do with the lack of oxygen and due to its bottled source is easier to work with then a large forklift sized air dryer needed for standard compressed air. Plus at most races involving changing tires, including nascar, a couple of large nitrogen tanks run the pnumatics rather then trying to setup a large high volume multistage compressor running off a gas engine or a 220v 30A circuit.