I would say cable TV coax has quite a lot more capacity than what the providers let on. In my city they offered up to 50mbps at over $100/month. Then they lost their lawsuit trying to prevent the city from installing its own fiber network and suddenly the cable company decided they could offer 150mbps for around $75/month (with no equipment changes). Once the fiber network started becoming operational (offering 1gbps bidirectional for$50/month) the cable company decided they're better also offer gigabit connection speeds, but once again they simply flipped a switch to increase your bandwidth. This capability has been in place for quite some time, they just didn't want to offer it and their illegal "monopoly" gave them no incentive to provide competitive speeds.
*I say "monopoly" even though we technically also have DSL available in town. However when I asked one of the techs why DSL couldn't give me more than 896kps upload speed, I was told that the cable company had an arrangement with them which prevented the DSL from providing the speeds needed by businesses. After the lawsuit that broke up the state-wide bans on other providers, this practice was exposed and also broken up, so now the telco is able to max out their DSL speeds.
They don't want to admit they've been screwing us over even though we all know it's happening. All these companies could have rolled out suitable internet speeds a decade earlier but they would rather limit everyone to the lowest common denominator so they don't have to admit just how terrible their equipment is in most locations.
I've gotta say, having city-owned fiber is great, folks here don't have to wait weeks for Comcast to send out a tech who conveniently never shows up on the scheduled day, and customer service actually has a clue what they're talking about. This is how a public service should operate.