Scala had a lot of influences, but the first two papers on Scala have references to SML and Ocaml but none for Haskell[1]. Make of that what you will.
> Leading more in terms of influence than usage.
Is Haskell influential? By what metric? Impact factor of papers published?
Here are some features that Standard ML had which were cutting edge:
strong static typing
automatic type inference
exception handling
pattern matching
parametric polymorphism
first class functions
Basically all of these features are features any compiled language would enjoy today. SML is a very influential language despite not being used much in industry.
Here are features which Haskell is known for aside from the above:
laziness
strict immutability
do-notation
typeclasses
operator overloading with symbols like +++ and ==<
Of these, typeclasses are wicked and influenced Rust's traits (the rest of the language being heavily influenced by [oca]ml). The rest are not even desirable. Haskell doesn't seem very influential in comparison. Maybe it's influential because it warns us to not default to laziness or go full strict immutability?
This is distinct from e.g. Erlang where the features like process management through the supervisor, mnesia, and so on are highly desirable for any developer even if other languages/platforms haven't implemented them as a standard component. (, vs . for line termination, not so much).
Most of Scala is derived from Haskell and even now the ecosystem heavily looks at what did/didn't work e.g. Cats, ZIO.