The little pizza dishes are too small for FTA. Being so small they have very wide beamwidth. This will cause them to pickup signals from multiple satellites at the same time and that's not good as the signals will interefere with one another. The little pizza dish companies can get away with using these tiny dishes because they use a different portion of the Ku band (12.2 to 12.75Ghz) that no one else uses and they space their satellites far enough apart and carefully use non overlapping frequency on sats that are close together. In others words they design their system from the beginning to be able to work with the tiny dish because it was one of the key selling points of their services.
FTA on the hand is totally different. Most (99.99999%) FTA services are not intended for home users to recieve. They're up there as a method of distribution to local affiliates, cable headends, and other secondary distributors like the Pizza dish companies themselves. So they're not concerned about making thier services easier for what they probably consider "unauthorized" viewers to recieve. Even if some of them don't care too much about "unauthorized" viewers, they're not going to go out of their way to make their signals easier for us to recieve especially when it means they'd have to sacrafice precious bandwidth by not using certain transponders with overlapping frequency on adjacent satellites. The people which they intend to recieve their signals have dishes of adaquate size to recieve the signal. That's all their concerned about. Drive by your local Fox affiliate and take a look at the dish they have.