Why do we have to put ourselves under labels?

Unfortunately that's how our world is. Most of us know that it's hurtful and stupid to categorize people without getting to know them but we do it anyways. Why? Because its easy to do it without realizing it and how mean it can be. I guess the best thing we can do is to ignore the catergorizers and try and set an example for them. Oh and I suppose people do it because it makes them feel safe to have groups of people so they don't have to deal with people who are different.