Builtin in derivation that is delightful to use—yes! ppx_deriving baked in, additional goodies for making printing/formatting simpler. The second for me, debugging.
I have influence in technology selections periodically at my company. I cannot sensibly offer ocaml as a contender in good faith without these. To offer this toolkit would reveal my bias, not my good faith argument that it’s a sensible engineering decision, knowing the hurdles to productivity.