Seems like a fairly straightforward solution to me. My assumption is that the powers that be aren't technologically sophisticated enough to understand the benefits of it.
This isn't the case, most networks are extremely technically sophisticated (ESPN especially) the misunderstanding here is business related. TNT and ESPN make millions (in ESPN's case billions) a year in subscriber fees from cable operators. ESPN alone makes $3-5 from each cable subscriber in the US (there's about 120M of them) each month. A significant portion of these network's revenues are made on subscriber fees. The solution you propose jeopardizes these agreements for what would currently be a paltry amount of streaming ad revenues.
If they want to cut out two middlemen (the network and the local cable provider) then the NBA must learn to create a steady audience and get money from advertisers, which is a different skill than putting on ball games.
Not "some" all of NBA's TV Revenues come from selling the rights to networks. The networks sell the ads, and they're the ones that care about eyeballs. So the networks care if you start streaming local market games and they're going to try to prevent that. If the NBA allowed you to get your local market games via streaming it would undercut the product they sell to the various networks which is their primary source of revenue.