Types help prevent a narrow class of errors. They also help with refactoring. They help avoid messy checks getting in the middle of your business logic. All of

Types help prevent a narrow class of errors. They also help with refactoring. They help avoid messy checks getting in the middle of your business logic. All of this is more than enough to justify using them. Types do not replace other checks and tests. I don't think the Mars satellite crashed because they trusted the type system.