Having a non-standard size is exactly the reason the tab character (not the key) is unusable. If you accidentally get some space indenting anywhere in the same project as tabs, then it'll be misaligned on someone's editor and they'll "fix" it, making it misaligned on someone else's. Trying to never use space indenting is impossible. Never copy and paste from anywhere else, never manually align multi-line statements, never align comments with code, etc.

I didn't even consider that, I just assumed we're talking about text editors.

But yeah I guess, that's another argument against getting accustomed to tabs for indentation.

Little irritates me more than logging into a new system, opening up code in vim, and witnessing the insanity of tabs-as-8-spaces