I totally agree - but in reality, parents today don't typically make that kind of rational, well thought out judgement call. Toon and Nick are the resident babysitter, and if it shuts up the kids, they can't live without it.
The channels you listed, along with all the children's programming required by the FCC's KidVid requirements from all the local broadcasters and the dedicated kids programming on most markets' PBS subchannels, provides more than enough children's programming.
Couple that with the advent of the DVR, and you should have enough programming to cover three times as much television as your kids should be watching.
Having said that, I still think those two are necessary for widespread consideration.