AA never has gotten into the paint business. The A300's used to be painted because AA didn't want to wait for the kind of milled aluminum needed to get the nice polished look. AA found a way to polish them and now they no longer wear paint either.

As to why no one else has gotten on the bandwagon? And this is just flyastrojets' postulating a bit... it has more to do with the egos of marketing execs and CEO's at the airlines than anything else. Branding of an airline is a big deal, and most tend to think that they are sending a big message with the paint on their airplanes.... i.e. US used to have polished planes too, but with Steve Wolf's repranding to US Airways, they went to the dark dark blue tops and grey bottoms for their jets.

Paint can certainly make a jet look nice, but I vote for polished aluminum. Looks good, saves weight, and makes maintenace easier too.