Also, DOCSIS 3.1 has improvements for bufferbloat issue and it would stabilize the current latency issues. They're not ignoring it completely.
If we do what you suggest, we'd be stuck at 10mbps for a long time and instead, we're getting 100mbps bandwidth that does work for your typical usage of netflix, gaming, and so on in a family household. There's a limit we'll reach very soon where no one will care about more bandwidth but they will want rather stability/latency improvements. Data caps is the next biggest issue.
A lot of execs from DOCSIS community agrees that 3.1 is the last upgrade to DOCSIS standard and the next replacement would be a Fiber-based one, which will take a few decades to even figure out. I rather have DOCSIS 3.1 now and not in 10 years because you think we should not do this.
Our US congress had the chance to fix this back in 1990s and they screwed up with enforcing it properly. We could've had a better pure fiber-based national build out but it didn't work out.