NBA players also have to market themselves. AI's image has worked out quite well for him financially (shoe deals, video game covers, etc.), and he is one the most popular players in the league, consistently selling out the arena in Philly despite being on a pretty mediocre team.
I think if, say, in the 80s, Larry Bird had showed up to games wearing t-shirt, jeans, and work boots (I don't know what he did wear) the media and fans would have fawned over it, like "hey look at this regular, average Joe...he's so *blue collar*!" Just like they fawned over how we worked on a garbage truck.
But Stern has to market toward where the money is. And the money is with all of the surly old curmudgeons who are afraid of baggy jeans. Stern already tried to market a "hip-hop" league and I guess that was unsuccesful.
Here's some more background on this image turnaround:
6 Jun 2005 Sporting News
http://www.sportingnews.com/experts/sean-d...y/20050606.html