I think it's kind of sad that, with all of the services offering an object store, nobody has created a better API standard than cloning the weird and clunky S3 API.
The problem is not that nobody wants to create or use such an API, the problem is that so much infrastructure and tooling is built up around the S3 API that to forgo it would be to leave your customers high and dry when it comes to integrating.
I think it was the creator of Java that said something to the effect of "There are languages people hate, and languages people don't use", which I think is very applicable here!
