unity-control-center depends on ...

Yes, gnome-bluetooth is declared as dependency of unity-control-center (at least for Ubuntu 20.04; you did not tell which Ubuntu release you are talking of)

"I can't uninstall just gnome-bluetooth..."
Why do you want to?

I don't need any bluetooth

Why do you care about software that is there, but unused?

There are lots of drivers in the kernel packages for hardware that you don't have. You cannot get rid of them either.

Just ignore it.

This is just irresponsible. These packages are wrong.

Please provide more details. What is wrong with them?

Why Bluetooth is a hard dependency instead of suggestion. Who made these packages?

Does this create any problem on your system?

This increases disk usage and creates many unused files... I wouldn't use unity-control-center package next time.

If packages are broken, then it is time to fix packaging. Installation of Bluetooth, Wi-FI "just in case" is not an option for some of my PCs.

I need to keep system images slim to decrease backup size and backup time.

It also affects how quickly the system can be restored from a backup on a new PC.

This is not a theoretical problem, count each megabyte as 0.005-0.01 seconds.

I suggest that you create a bug report, clearly stating:

- what you expect to be changed (preferably in form of a patch or debdiff)
- what the benefits of that change are
- and provide a proof that there are no negative consequences