Comment by eridius

Because it will completely screw with anyone who actually wants it in the per-repo config file. If I'm new to git, and my first usage is on a sample project, and git prompts me then I'll put in my personal contact information. But then if I go and start working on my company's git project, it will never prompt me again and I'll accidentally be committing company code under my personal email address. And I would be perfectly justified in blaming git's faulty user interface for letting that happen. At least if I set the config myself I _know_ I'm placing it in the global config file.