Why do we generalize

I get really annoyed at all these posts and memes the generalize life. No two people are exactly the same, which means not all men act the same, not all women act the same, not all whites act the same, not all blacks act the same, not all gays act the same, not all heteros act the same, not all young people act the same, not all old people act the same, and not all anything acts the same. We generalize everything and then can't understand why no one understands who we are. We label everything so nothing can be the big scary unknown. Well guess what, I'm unique, just like everyone else. ;-)