AT&T and Verizon has proven that they can and will abuse their oligopoly position and not compete. This will not change in any foreseeable circumstance short of being forced into a competitive landscape. The duty of government then is to lower the barrier to entry, which, in this case, the barrier is the amazing amount of cash AT&T and Verizon has to outbid everyone else.
And if you object to taxpayers subsidizing, then I can simply point you at the cost of running any government agency that (ostensibly?) promotes fair competition: e.g. SEC. The cost to hire lawyers, set up offices, conduct audits, litigate -- none of that is free. Do I see you label "preventing and punishing insider trading" as an "interesting debate since it has no objectively correct answer" in a cost analysis? No, of course not, because it's desirable and everything has an associated cost to begin with.