First off, I like your avatar. Get Fuzzy is the best comic out there right now.
Unfortunately, I have to disagree with what you just said, however...
If it was all about maximizing marketing money, then the league could force heads coaches to be decked out in every possible piece of licensed apparel. Team socks, headbands, armbands, pants (Zubaz preferrably), sunglasses, gold chains, watches, etc.
At some point, though, the coach looks like a walking billboard and the extra marketing money is not worth the cost. It seems like it may be worth it to forgo the minimal reduction in licensing revenue in order for a coach to be able to look more professional to his team.
If wearing team apparel is so crucial for a league's success, then why don't they do it in hockey and basketball as well?