First, it’s a pain to get many of the Japanese studios to release the material. Second, it takes a lot of effort to get them over-dubbed and it’s not cheap either. Plus, they tend to work in bursts so it can be a while before the next batch is released for another market, and then starting the process over again.
Well, maybe you CAN blame Cartoon Network. They have a habit having some of the worst programming directors in the history of bad television. They yank stuff all the time for no reason.