Why do people always get underestimated just because of how they look, or what hey wear?

Have you noticed that some people that do not look intelligent are actually some of the most intelligent people in the world? Albert Einstein may have had some crazy hair, but that does not change the fact that he was very smart. This is why we shouldn't judge a book by it's cover. We can't just look at a person and instantly make assumptions about them because of how they look or what they are wearing.  Everyone should get a chance in life to accomplish what they want to accomplish or try out for what they want to try out. We are all humans and we all have our flaws and  mistakes.