So that when someone used to tabs, does something in a spacebar-project, they can see that they will need a clang-format.
Oh you use an indentation sensitive language? Err... my condolences.
They might be working on an old codebase with maintainers who yell at you if you try to standardize formatting because "whitespace changes pollute diffs" (smh, programmers who don't know how to configure their diff tools).