"That's strange. I've always had the opposite impression - that they maintain compatibility at all costs, including leaving sub-optimal APIs in the standard library."
When I started using OCaml, many standard library functions weren't tail recursive---you couldn't get the length of a list with more than ~10,000 elements, for example. The library definitely seems like an afterthought compared with the language. (And that would be why there are so many of them.)