They may not have any competition within their municipally-granted franchise authority - but I can virtually guarantee that their monopolies are in jeopardy when the neighboring cities get gigabit from Google, Cox, Verizon, CenturyLink, et.al. Local franchise authorities are well aware of the technology that's available, and are applying pressure to get it. They're also aware that their cities grow when the infrastructure is there.
And if you're a household in one of those communities, I suggest you contact the local franchise authority and complain. Squeaky wheels get the grease.
Comcast is slow and shitty and definitely won't hit their "goal" - but they're not completely stupid either. They're just following trends.