Oh please... HBO is owned by Time Warner, who is in the cable business. They have absolutely zero interest in promoting cable cutting, especially as HD cable with a standard decoder box and basic cable is going to set you back 50-60 bucks a month, and usually runs closer to 100 bucks a month. HBO is a loss leader at that point.
The premium channels drive cable subscription, which is where the money is. You'll never see HBO Go on it's own or sensible a la cart charges. That defeats the entire purpose of renting you a cable box and charging you for 400 channels you'll never watch.