I don't believe faster internet is the top priority of most American ISPs. This is the quality of a monopoly- the focus on maximizing profits. It's not that having faster internet is bad for them as much as it's a waste of time and money compared to simply milking their existing monopoly.
And make no mistake, ISPs are a monopoly. Due to 1) the inherent difficulty of building a broadband network 2) a hellish patchwork of local regulations and government-granted exclusivity deals, ISPs function in a state of basic monopoly.
Densely populated areas can have multiple options for high-speed internet, but the market is not bursting with competition.
If you don't have to compete, what's the point of building out faster internet? Why spend more on investment without competition? Why not just focus on making as much money as possible off previous investments?