Your average cable is some wire, some connectors, and plastic. Adding a resistor adds a whole extra element to the process, which is a big deal for a part that sells for probably well under $1 wholesale. Cable shops probably have no experience with circuits. The USB-C spec for some reason made it so that cables with no resistor or with the wrong resistor still seem to work but are unsafe. Of course the result is a mess.
Just about every video game console made between the late 1980s and mid-2000s had an official video-out cable with one or more resistors [1]. It's not an unheard-of thing.