Why don’t CLI tools just use a Web UI?

For example, Codex CLI—
why do you have to use a terminal TUI?
Clearly, the ChatGPT Web UI could connect via a local port on the machine, and that way
things like multitasking, forking, etc. would be much more convenient.

Right now there are so many forks in Codex’s CLI that even finding the number of tasks takes forever.

Also, OpenAI went and reinvented the wheel again with something called Codex App—so the UI changed.
In fact, it could completely reuse the ChatGPT Web UI.
I don’t know why they didn’t do it that way.