As someone else pointed out, it's object storage not block storage meaning things like partial reads and partial writes don't work. That may not be a problem for you, but it _is_ a problem for me (particularly when dealing with remote data).

> for which there exist multiple utilities to mount the thing as a local file system

Which all have their own sets of intricacies. The most obvious one being listing a directory is either impossible, costly, or as slow as the heat death of the universe. Other (far riskier) ones (from s3fs-fuse, which I have the most experience with[0] ) are the lack of guarantees about atomicity and concurrent access.

[0] https://github.com/s3fs-fuse/s3fs-fuse