It's a classic case of frustrating customer experiences pushing users to piracy. If the NBA provided a way for me to legally pay to watch every game over the internet, I would gladly do so. In order to legally do this I have to have both a cable or satellite service in addition to a league pass subscription.
I understand that a fair amount of revenue for the NBA is probably coming from the deals it made with TNT, EPSN, and Fox, but a viewer is a viewer, whether they're watching from the net or through traditional venues - why do they care, so long as their advertisers are getting enough eyeballs?