But consumers *have* asked this question
The real issue is, how does the consumer fight off the huge telecommunications lobbyists in Congress? The massive amounts of money being thrown around work against the average consumer who wants more choices in the wireless marketplace. Simply 'going prepaid' clearly isn't going to work as a solution for all.
Shared family data is just around the corner though, at least for some US carriers. Not sure about places like the UK or India.
The other issue you have forgotten about is how much the carriers have to pay Apple for the iPhone. It's crazy money. To recoup only part of these fixed costs is difficult, even with mandatory data plans ("tariffs") [in the U.S., this would generally be referred to as 'additional fees'].