I'd say it's a reflection of an earlier stage of interpersonal maturity to try and put people into categories. More socially attuned people realize the complexity of other people and situations and synthesize all the available information to make a decision that is truly reflective of reality.

It's interesting to think how this affects self-perception. Basically this applies to how one views and treats themselves. One approach is to read book, take a test and put yourself in a bin: "well, I'll never be able to do xyz, the book said I am an abc". There is a danger there self-limiting and making the same mistake putting others in bins.