The whole business is fishy as hell. 29 states and in not one single location do they compete. The only reason they get away with it is because
they were banned from entering the market the other company was in when cable franchises were handed out in the first place (well, in most areas, they were banned from entering even the markets they are in, but they bought the companies that had been granted the franchise for that area).
The problem exists because our government created it. The cable monopolies did not start with the cable companies (although they worked to encourage it once it started).
While Comcast and Time-Warner could possibly have overcome this restriction to compete with each other, why would they? What would they gain from spending the amount of money it would take to overcome the regulatory obstacles to competing with each other? The likelihood of smaller profit margins and the significant possibility smaller total profits.