I don't like Government wielding a heavy hand in business.
Towers aren't free to build, run, network, lease or buy the land they sit on.
There has to be an economic benefit for the companies to place them, or they don't.
While it would be great to have total coverage, you're still dealing with low-power rf signals. The number of towers necessary to cover 100% of those areas, not to mention added height, is a lot more than you think.
So how much would it drive up costs for EVERYONE, not to mention the eyesore of having hundreds, if not thousands of new, significantly taller, towers sprout up everywhere?
Also consider that the decision to live/work/play in remote areas bring responsibility for the consequences of said decision. Longer response times, less or lower quality access to some communications lines (like cell coverage and internet), fewer choices in retail stores, etc.