The lowest common denominator is the same reason that Bluetooth outside of the Apple ecosystem is such a shit show.
Android has supported its own proprietary video over micro USB for ages before USB C became more ubiquitous. What are the chances that Android manufactures won’t cheap out and not ship with cables that can support video over USB?
and I am probably overestimating by order of magnitude.
Most people shoot photos and show them to their friends online. Some of them even share it through sites like Instagram and Facebook or WhatsApp and similar.
And that is where it ends for most normal people.
As long as the cable can charge the phone, it will do for the most buyers.
I know the "standard setup" shown in media, and advertisements, etc shows a ring light with a cellphone using the front facing camera as the recording device, that's just not technologically feasible.
And for the record, i move 4k and/or 108MP images from my phones via wifi or cellular, using synology diskstation autosync or syncthing, respectively. I've used syncthing to upload unedited 4k30p drone footage with no issues, and when i get home, it will sync to hard disks in addition.