It's a problem because as we've already seen, if AT&T or Verizon makes a business move, the other "reacts" to it and the reaction is usually it's beneficial to both parties and not to the customer.
The basic principle of regulation is missing from the US regulatory puzzle. You have a market where the telecommunications companies function as their own regulators. They set their own prices, place their towers where they can make the most money (particularly AT&T here)/screw expansive infrastructure and actual mobility, stipulate the kinds of phones that are on their network, and create a barrier of entry revolving around contracts/subsidies and credit checks. Spectrum allotment is an obvious technicality so everything works but in this case, it's a fancy way to pad and line a few wallets.
It's super cozy if you can set all the conditions and variables in your market and be the one or two companies in it. FCC and FTC basically function as agencies willing to do anything for the highest bidder and the companies only care about themselves. The problem is obvious; the customer is completely left out of the equation. It's not a free market and if it was, it's been perverted out of one.
Somewhere, somehow, it hasn't been made an issue, yet. I wonder if and how AT&T will work up the muster to get rid of it's unionized workforce with this acquisition/merger, if it does happen.