If a founder of a lunch restaurant starts out by saying "hello everyone, I'm here to make the best lunches possible but only for southern white people" I suspect, given my experience with lunches on three continents and in 37 states in the US, that he is going to have a hard time finding people who would actually be able to make good lunches.

Which is the point.

This does two things: it focuses people on what the actual mission of their company is or should be, and it can expose the kinds of missions that are nuts, or counter-productive, or just plain bad.