Why do I need to meet the same person more than once.

So I was thinking about groups of people and how some sub groups share so many similarities that the people associated with that group seem to be nearly the same person. Some of these sub groups are very large if you remove outside appearance as a distinguishing characteristic. If you can that is. It seems reasonable that how a person decorates themselves on the outside is a representation of their personality. Hmmmm If the person puts little thought into how they dress themselves or doesn't dress themselves with any form of expression what does that mean?