It's an arbitrary choice in the Prelude, yes. If you don't like it you can definitely your own Cons type (or wrap a list in a new type) and define any monad instance (semantics) you choose.
Cons/lists don't have to be involved at all: a Set type could be made to work for many applications.
I've observed several smart people struggling at the outset with the connection between recursively defined lists and nondeterminism in Haskell. It's not uncommon for people to assume that there is some essential connection between the two, because that's what "list monad" seems to suggest. In fact any collection type would do.
