Interfacing with older APIs that don’t support unicode can be a pain. Too often I’ve seen errors from third parties saying:

Error: characters must be in the range 0 to 127.

Suppose that we’re writing an API for some site that internally will be interacting with these types of third parties. This API will allow people to create users and sign up. We want to allow people to sign up with their real names with accents and all (such as José), but still only give third parties ASCII characters.