Why else institute 300GB data caps when there is no problem with congestion, and make incremental charges for exceeding those data caps at $10 per GB? Why else

Why else institute 300GB data caps when there is no problem with congestion, and make incremental charges for exceeding those data caps at $10 per GB? Why else roll-out their own streaming service that doesn't count against those caps, and allow other major players to pay them for that access? They're positioning themselves to continue to cash-in on those wishing to access television-like content.