Google Voice offers for free some features that compete with services that AT&T charges for.
Yet you still want full access to AT&T's network without them saying anything.
Again, let's get Google to subsidize your iPhone. Because I'm sure Google will have no problem
maintaining that hypothetical cellular/data network of theirs by offering all those
free services. Not to mention that subsidizing a phone like the iPhone costs quite a bit in the first place, as well as maintaining a technical service/customer support infrastructure. But Google can pull it off because they can pay for all of that with the money that drops out of the clear blue sky.
Google is not a carrier. It has no cellular/data network to maintain along with all the associated services that customers expect. Google doesn't have to subsidize data-intensive smartphones. They can simply waltz in an offer a set of services for next to nothing, and for some reason, you as the customer expects AT&T to pull off the same trick, and when they can't you complain about it.
Or if you think that the company providing the network should be separate from the company providing the services on that network, then who are you going to call when something goes wrong? Who gets to assume the blame? Will Google's breakdown in service be blamed on innocent AT&T's network, or vice versa? How do you propose to achieve a separation of powers?
You want AT&T to function as merely a bare network? Fine. Then be prepared for neither the carrier nor the plan-provider (since they are now separate entities) to assume any responsibility for the other's issues. I'd love to see this scenario in action and the kind of customer service "situation" it would cause.