It's a little bit chicken and egg too, but the NFL doesn't have any "local" media(aside from Radio which I believe the team's actually keep.) But because the NFL TV and internet deals are sold as all or none, then there truly is no local media contracts.
On the other hand, in baseball, 30 different teams are selling 30 different ad packages. Not only does this cause the networks to spend additional money overall(there are two sets of announcers at virtually every game) but on some level it encourages a company like DirectTV, which has a significant stake in the Fox Sports Network, to attempt to keep individual contracts low. They don't want FSN Milwaukee to pay $100 million and FSN Cincinnati to pay $50 million. Soon the Reds will be demanding a deal similar to what the Brewers get. Meanwhile, teams who do not have a deal with FSN(name the city) get more money because their networks are dependent on the teams doing well. YES network in particular probably has a vested interest in raising the Yankees competitive advantage.
So on one hand, the baseball system is inequitable, on the other hand, it probably brings in more TV revenue than it could otherwise.