They generally do not wear neck ties. As much as you may wish we could all just love each other, the truth is that a small minority of humanity is out there trying to steal from us, rape us, and kill us. Because of them, our defenses must be stretched out to some degree at all times. We listen for perceived insults between the lines of what we hear, and we watch for signs that someone may be in a situation that would drive them to commit a crime. The truth is that it is impossible to stop judging people by what they wear, how they talk, and whatever stereotypes they fit into.
Exceptions exist to be sure, but stereotypes are the norm.
If they were not the norm, they could not exist as stereotypes. The same is true of strong accents. Having a Southern accent, for example, is considered evidence of a poor education. Often people with strong Southern accents are scoffed at before they can even present their ideas - no matter how educated they are. As a result, one of my school teachers used to constantly correct me and encourage me to ditch my Southern accent as soon as possible.