Redundant physical networks using the same technology are a vast waste of capital.
It's the same reason we don't use separate networks of water or electricity. Internet really is the same thing, there are exactly 2 things that matter (assuming it's working) bandwidth and latency though you can easily degrade service via network design etc.
Unfortunately, this results in monopolies which means either public utilities or wasting capital on redundant networks. Globally you see a wide range of approaches to the problem, the US seems to be basing things off of it's healthcare system aka mixing public funds with private enterprise.
It's the same reason we don't use separate networks of water or electricity. Internet really is the same thing, there are exactly 2 things that matter (assuming it's working) bandwidth and latency though you can easily degrade service via network design etc.
Unfortunately, this results in monopolies which means either public utilities or wasting capital on redundant networks. Globally you see a wide range of approaches to the problem, the US seems to be basing things off of it's healthcare system aka mixing public funds with private enterprise.