The telephone system extensively uses coaxial cable to multiplex phone and TV signals. Indeed, the phone co has been carrying TV signals for years. The telco could've integrated cable signals into its existing plant and billing systems. There would've been definite economies of scale to be gained if they used telco standards.
I've seen and dealt with cable construction by various companies. To say "non union labor" is an understatement. Cable companies got day laborers off the street and ragged 2nd-hand equipment. Lines were strung on poles FAST. They disregarded the wishes of communities and shoved their work through, irritating the heck out of property owners and towns, knowing once the work was done the town likely wouldn't litigate. Cable reliability is far less than phoneco; their underground lines are very shallow.
Cable used existing infrastructure -- the same poles power and phone lines already used, they just added theirs. Because the cable is a common signal, it is much simpler to run than providing a unique channel for each subscriber.
So, either the costs of cable are so high that the phoneco should've done it to provide for economies of scale, OR, cable laying isn't so expensive that others couldn't do it too.
I dare say VOIP and other value-added services were in mind when they went to fibre (another rush job).
A great many phone subscribers do not have a dedicated pair of copper wires between their home and the CO. There are various ways of multiplexing the line (see the discussion on party lines) plus the use of concentrators. The Bell Labs history and "Bell Labs Record" describes many of those techniques. As mentioned, telcos know about coax and TV.
Telcos couldn't do so because of a policy decision, not a technical one. The long distance network was built to carry voice, TV, and radio. The local loop can be set up to carry high speed data and at one time could carry pulsed signals (not modulated) for Teletype machines.