It's not clever for its own sake. Haskell is rooted in math and Either is logical disjunction. Its semantics is precisely that. Error handling is a specific use

It's not clever for its own sake. Haskell is rooted in math and Either is logical disjunction. Its semantics is precisely that. Error handling is a specific use-case that can be implemented with Either. Rust as a language is more pragmatic. In real-world industrial code the concept of Either is predominantly used for error handling and thus Rust named their data constructors aptly.