Re: low population density
A sensible government would have mandated 100% coverage by all networks in the first place
That would never have been economically viable, so the operators would have asked for government money to do it. Either taxpayers would have had to pay, or the 98% with good coverage would have been paying for the 2% where almost nobody lives. After all, you can't get landline installation in 100% of the country either, at least not without paying extra for it.
Mandatory roaming in areas where only one operator exists would be a better solution.