"The Golden Mile" problem. There's a certain "Break even" point with efficiency vs population density involving cost per user to maintain. Pulling numbers out of the air to explain, it comes down to something like the provider having to spend $10k/yr(probably more than that) to run a switches and repeaters and string a line to get Bob, who lives 5 miles away from anyone else, his internet that's only paying in $75 a month. Whereas if you had 100 subscribers all on top of eachother, your marginal cost per subscriber all gets absorbed.