The joke is that this is the state of American TV and Internet.
Sure some Cable ISPs let you bring your own modem, and Verizon Fios used to let you provision the Ethernet handoff of the ONT to go direct into your own router (if you chat up the install tech and are able to test connectivity with them there)…but the majority of users rent their modems and cable boxes.
Remember when you had to rent your phone from the phone company?
Imagine if service providers still did that now, and you’d have to rent a special box from the internet company to access the internet…or one from the TV company to watch shows and movies. What a world.
That’s so easy to answer though. They’ve been using the explanation for a while.
“God made science to test our faith”.
You are conflating layer 1 technologies (shielded or unshielded twisted pair, CAT3 through CAT7) with layer 2 technologies (Ethernet).
Layer one is the physical media itself. Alternatively some modern-day L1s are MoCA, Powerline, WiFi, fiber, and of course, 1000BaseT, whose standard specifies CAT5e or higher STP.
Layer two is how those bits get sent in that media. Ethernet is, by and far, the most familiar L2.
And then layer three is where we get to networking and start talking about IP addresses (IP being the most familiar L3).