Because it's a comment that has no bearing on how the code works. If you make another change to that same file, feel free to update the comment as well. PRs that do nothing but fix a typo in a single word in a comment are useless. Maybe if your PR has several cosmetic/docu type changes throughout once the codebase is stable and working, I could see a pass going through to clean up things like this. However, as asked, no, it is not useful.
