why do you need so many channels on a jet?

im planning on getting a good radio soon, and it seems most people use most of there 8,9 and 10 channel radios, how can you use so many channels on a jet?
its gonna be a while before i can afford jets, but for my other planes id like a quality radio, and id like to only buy once.
im thinking hightec, i love there products, but 7 channels doesnt seem like enough.