It's not the backhaul that is the chokepoint. It's local nodes near your house. The one you share with 50-100 homes or more.

A Netflix "ultra HD" stream requires 25Mbps. Even if all 100 homes are simultaneously streaming ultra HD, that's 2.5Gbps in total. Coax can handle that easily with modern equipment.

Obviously they could be using very old equipment that can't, but whose fault is that?

Cable companies can't replace network hardware every three years. It's just not profitable. Cable systems were upgraded to broadband 2000-2005. 10-15 year replacement is short in the telecom industry. It's not surprising that new entrants into the market can give much higher speed. If you demand upgrades every 5 years that is going to increase costs considerably.

Also a large amount of coax spectrum is for video tv service.

The real curiousity is why Verizon fios can't deliver near 1gbps. It's already has a fiberoptic network. I'm guessing it's the hardware at the nodes.

Quite so. Usually the same in mobile networks, but sometimes backhaul is a limitation there still.

It's getting a bit ridiculous. ISPs have pocketed multiple rounds of order of magnitude jumps in network technology while customer speeds have stalled and "usage caps" are on and off.

And that's just the "assume they are not acting in bad faith" stance; we know they are willingly not upgrading the interconnects to (eventually) Netflix and others, who their customers are requesting more and more data from.