DOCSIS 3.1 allows it on paper, yes. But in the real world, bandwidth is a huge constraint, especially if you’re also serving digital cable. No cable ISP in North America today on D3.1 has a network that can support it even if they wanted to.
For example, Comcast has 4 upstream 6mhz sc-qam channels (which is basically using none of the advantages offered by 3.1) and 32 downstream, and their video service is 720p across the board and overly compressed. They are constantly trying to free up data channels and migrate to newer codecs, and eventually go to IPTV, but that requires changing hardware both in their network in the customer’s home, or the customer’s TV goes black and their internet goes out and you get to hear their rage when you tell them they have to spend a few hundred dollars on new cable boxes/modems so that Comcast can build out their network. It’s a massive infrastructure upgrade to use DOCSIS 3.1 to its full potential that is further complicated by a need to support all of the legacy hardware during a transition.
Add to the mix that upstream channels are far more susceptible to unwanted ingress, most homes are full of amateur RG59 coax cable, and it becomes a support/troubleshooting nightmare as well. When you get into higher upstream speeds, these deficiencies become a much bigger problem.
I have observed speed tests on an uncapped docsis 3.1 modem on the comcast network getting full bandwidth on all channels, and it was still way below 100mbps upstream (around 80mbps).