There are some industries that are natural monopolies, like water and electricity, because it's incredibly expensive to build both last mile connections and core infrastructure. They're also natural monopolies because you don't really have great, cost competitive alternatives to water and electricity provided on a large scale.
When you consider hard wired internet, it bares of a lot of similarity to utilities, in the cost and difficulty of accumulating infrastructure and in the absence of effective alternatives.
For that very reason, internet should be classified, like other natural monopolies, as a utility.
Moreover, last mile lines should be rentable or available through competitive bidding. There's actually enough dark cable to make some regional ISPs viable if they could actually get access to consumer level last mile lines. But Comcast won't get off them unless they're kicked off them. And if you try to build lines then Comcast will half their rates in the areas that you offer service in!
Of course, Ajit Pai will have a lobbying job earning well north of 400K the moment the Trump administration runs out the door so it's really not his concern.