[elithrar]

Cost. I would also say that most of the 'cable' is laid inside conduit, but conduit with limited space and owned by a particular carrier who has no incentive or regulation dictating that he share that conduit.

[jeffool]

Now i can't help but wonder, would it be wise for the government (likely local) to lay pipe and license room in it to ISPs? Much of it could even be done when working on sewers and roads, I'd imagine.

(Cue complaints of government interfering with business.)

[sapphirecat]

You might find your answer in the history of municipal network projects. But I'm strongly biased against the incumbents, so I'll avoid leaving any details here.