they did. Its called being an MVNO but we've seen that those don't work. You can't piggy back on someone else for ever and the MSO's don't want to build out a new network; especially since in one state you can have 4 or 5 cable providers and they only cover a small area.. Those companies would need to build a network together and share it. And that won't happen. They created this company to make the $$ back that they wanted.
The only real option for the MSO's is to buy someone out and that could be Sprint-Nextel if China Mobile doesn't buy them up.