Better cable doubles reach. Calix used a 16 port fiber-fed distribution point to deliver 500+ megabits 2,000 feet. For many years, American builders have wired homes with coax, most of which are served by the local cable provider. But 8% of the U.S. does not get cable broadband. If coax is in place, Calix has just demonstrated an alternative.
In addition, some developers prefer to maintain exclusive control of broadband. G.fast over coax could be a tool for a non-cable company to compete for the business. Within a building, there's a pretty stark performance difference between G.fast and VDSL.
If you have fiber to the basement, anything but G.fast is obsolete by the end of 2016 and possibly sooner. BT is proving G.fast works in the field