scy on Nostr: Because it's often hard(er) to read, contains characters like underscores or numbers, ...

Because it's often hard(er) to read, contains characters like underscores or numbers, or smashes parts of the name together into one word. For example, people who are using their passport name may have something like "peterparker@instance.example", but would really like to be called "Peter Parker".

A handle is a technical reference. In contrast, the "name" field's whole purpose is to specify how someone would like to be called by actual humans.