Fault tolerance and declarative programming. It's easier to write code that clearly expresses your intent when you don't need to clutter it with error-handling

Fault tolerance and declarative programming. It's easier to write code that clearly expresses your intent when you don't need to clutter it with error-handling code. Likewise, pattern matching completely eliminates complex layering of nested 'if' statements, and is an alternative solution to the kinds of problems typically solved with polymorphic dispatch in OO languages.