merry go round..
the basics are: speed, quality of service and price...
sure, if you can deliver 100/100 symmetric with 100% uptime qos guarantee for a lower price under docsis than fiber, by all means.. select the chocie that's right & cheaper. brighthouse does not serve tens of millions of customers beyond Floridia.. if they did, they'd REALLY see how difficult a job to make an all fiber network would be. Verizon isn't stupid for cherry picking it's customers when the upgrades cost BILLIONS... however, they've got a network in place for the next 20+ years. perhaps wireless will become as robust, that remains to be proven as well.
the truth is docsis is cheaper for more than the face value of deployment coax vs fiber. in reality, the labor is about the same price.. the cost of the fiber is negligably higher priced, but a "cable internet" plant is also managed differently for business vs residential customers. business customers can select from two, and sometimes 3 levels of QOS.. obviously with different price quotes. most cable companies leverage existing coax in the field. to overlay and/or replace that with fiber would be kind of expensive and the uncertainty of a big fish such as Verizon or AT&T invading their market is a not too distant possibility.
Bright house would like to scoop up that monthly fee with a fishing line (coax), rather than a demolition ball grade steel cable (fiber). Any company using twine (copper pair dsl) such as AT&T/ Qwest will have to eventually spend more and more money to fend off competition & manage customer churn rates (should there actually be real competition in those markets)