The vast majority of Americans live in neighborhoods far more dense than that, even deep in the suburbs. I can't find the figures for America, but according to this presentation 100% of Europeans live within 500 meters of their distribution cabinet: http://www.wik.org/fileadmin/Konferenzbeitraege/2007/VDSL-Co...

I agree DOCSIS has been good enough. But with the shift to services like Hulu and NetFlix I would argue that it's nearing a threshold. And even if it weren't, I bet if a telephone company had somebody as highly motivated as Elon Musk, they'd be able to eat their local cable company's lunch.