In theory, they do. In practice, I have only seen one codebase — ONE — in all my years of programming that was using tabs and yet did not end up with spaces getting mixed in with those tabs at some point along the way. (In the indentation, I mean: obviously once the non-indentation part of the line starts, you want spaces there). And that codebase had precisely two people committing regularly to it. Occasional PRs from other contributors, but only two primary maintainers.

Every other tab-using codebase I've seen (of non-trivial size and complexity, that is), someone, somewhere, had been lazy, or had a misconfigured editor, or something, and spaces snuck into the tabs. The worst offender I ever saw was a file that had been edited by multiple people over the years, who must have had different tab settings in their editors. There was one section where they had tried to line up a bunch of variable assignments and values. (Yes, I know, bad idea, but stick with me for a minute, I'm getting to the punchline). None of the pieces of code that were supposed to line up were actually lined up. (This was C# code, so indentation didn't truly matter like it would in F#, or Python, or ... well, I won't list all of them since I'm trying to get to the point). Here's the really hilarious part. I tried all sorts of tab settings to see if I could get that file to line up. I tried 8. I tried 4. I tried 2. I even tried 3, the setting for the people who can't make their minds up between 4 and 2. Then I tried really oddball settings like 16, 5, or even 7. Nothing worked. There was no tab-size setting I could use that would make the code line up.

That was the day I said "Forget about tabs, just use spaces, you won't have that problem with spaces." Tabs have great promise, but in practice, in my experience at least, you end up having to tell your colleagues "hey, you need to set your tabs to 4" (or 8) "before editing this file". Which almost negates the promise of tabs. They're great in theory, but I've only seen ONE codebase that made them work in practice.