I think it's not common because primarily functional languages usually have dedicated syntax for partial application or currying, or just do it automatically. L

I think it's not common because primarily functional languages usually have dedicated syntax for partial application or currying, or just do it automatically. Languages not built around functional programming usually seem to consider this sort of thing suspiciously clever, so not having syntax for it is an intentional choice. ReScript just recently removed auto currying (inherited from ocaml) and instead added a very similar syntax for partial application. It just uses ... instead of _ for the arguments.