Because the best advertisement for their product is people who are actually into the product. You don't need to give away stuff to them to keep them interested

Because the best advertisement for their product is people who are actually into the product. You don't need to give away stuff to them to keep them interested, because the product speaks for itself. Furthermore, seeing more basketball around is not going to turn non-fans into fans. To do that you need something that transcends the sport such as a Michael Jordan or 2015 Warriors. Now, outside the US in places where NBA has not yet saturated your approach makes more sense, but you could also burn a lot of cash for no returns if you're not careful.