Many applications use s3 as a data store for... Whatever. Uploaded or generated files, intermediate outputs, as a key-value store for large blobs. You can put

Many applications use s3 as a data store for... Whatever. Uploaded or generated files, intermediate outputs, as a key-value store for large blobs. You can put all sorts of things on s3. The PDF containing your bank statement, your medical test results, whatever - S3 is plenty secure enough for that with sane configuration, and even by default with sane account management.