Depending on the project, doing a re-release with an appended or updated version number might be a huge hassle. For a small, single-binary program run by an agile team it's pretty trivial to recall a release and publish a replacement, but for larger open-source projects with long, complex, release processes, paying customers, external docs, etc., spending an entire new day doing an entire new release to fix one typo in one word in one file in one artifact is less practical than just re-uploading the file and updating your SHA256SUMS.