The informality is one of the American cultural values. They will wear something that they comfortable with, whether it is an old clothe or unfashionable or even out of trend cloths. The American life style or way to dress is originally casual. You can generally see American student wear short and t-shirt to school, or even the teachers, they would wear blue jean and comfortable shoes to their work .Furthermore, if there is a problem in their life, they would take it easy. Same as origin of Thai people, Thai people love to be chilled, they wear whatever they want.