Why are there so many channels that don't work

I should have said public channels displayed in the channel store. Several indicate they are not available or something else is wrong. Roku checks them before they are published but does roku ever check to see if they are still valid after a period of time? It doesn't seem so. The roku people should because it is a real pain to think some of these public channels are ready to go when they don't work for some reason. Don't you agree? Anybody got an answer?