The studios can't start their own streaming service simply because they do not have the branding they think they have. This isn't the 1950s, nobody thinks "I must sign up for MGM's service they have all the best action movies". HBO and BBC might manage to make separate pay-for services but are more likely to simply agree an extra cost deal with Netflix in the same way they sell an extra cost package to cable. Does HBO really want to get into the writing and supporting software player business?
Then the studios have a problem that they are in direct competition to their main customers - the cable companies that would be delivering these shows over IP. Can we say serious throttling?
Sooner or later somebody in Hollywood is going to manage to get the childproof top off their Lithium tablets and realize that iTunes hasn't quite destroyed the music industry.