They are invisible whitespace characters that are handled reliably and flexibly in every editor that I've ever used them in. The same cannot be said for spaces.

They are invisible whitespace characters that are handled reliably and flexibly in every editor that I've ever used them in. The same cannot be said for spaces. If a codebase is using two space indenting, I get to look at the resulting puke (this is subjective, of course) on my screen. I might be able to do some hackjob fix to change how they're displayed, but why should I have to? There's a character that satisfies both me and the animal that wanted to indent their code with 2 spaces.