Labels

Yesterday I heard someone accuse someone else of assuming that she was one-dimensional. I realized that I know people who do this. They make snap-judgment decisions about peoples' personalities and label them and shelve them away into some category relating to how they perceive the person's level of shyness, athletic ability or mental acuity, or some other category that could be easily imagined. (Insert sample label here.) People like labels. Do we truly deserve them? Or are we all actually complex, multi-dimensional creatures that deserve more? Or is the truth somewhere in the middle?
I can think of several occasions when people who have labeled me with one classification or another, say, for example, "nice," are later shocked when I do something that doesn't fit behind that label they so quickly assigned to me. They become confused, saying, "You've changed," or, "I don't understand you."
Why don't we give more credit to ourselves and assume that we all have layers of personality, instead of one shallow level of existence? Wouldn't that be "nice?"