Honestly, it's distance not population. 5-10 years ago you could make claims about Nordic countries or South Korea being only because they were small.
Really our providers have not significantly invested in infrastructure (beyond routers and stuff, I'm talking cable/fiber to the door) much in the last 25 years. You pretty much have the same cable going into many houses that was going in there in the early 90s.
Why not? Because we're not up in arms, we pay, and new fiber or whatever costs money. They're doing what they kind of should and soaking profits, until we get mad enough to not buy or someone like Google comes along and shoves them with competition.