I've always wondered, why does Android forks of Firefox are not (or cannot?) get rid of ALL the trackers? Even Tor browser!

The browser with the least trackers is Mull, but it still has 1 Mozilla telemetry tracker, which the devs claim is completely disabled. I can't really read and inspect code, so I don't actually know.

So why is it? Does Mozilla make the browser unusable if you try to remove the tracker from the code?