If you dress like a slob, you'll behave like a slob and people around will perceive you as one, while dressing sharply and professionally will increase the success of your performance:
If you want to be a big-ideas person at work, suit up. A paper in August 2015 in Social Psychological and Personality Science
asked subjects to change into formal or casual clothing before
cognitive tests. Wearing formal business attire increased abstract
thinking—an important aspect of creativity and long-term strategizing.
(From Scientific American)
So here you have it from the mouth of scientists, modern sloppy "casual" way of dressing decreases abstract thinking and destroys creativity, while dressing in formal attire produces "the feeling of power". There is a reason dress codes exist in business and finance and legal profession.
Now what does it do to a woman's self-esteem to constantly wear what was traditionally considered male attire and could at best be described as unisex clothing? Or for an adult man, husband and father to wear baggy shorts with flip-flops on a daily basis? Or for a housewife to spend her whole day in pajamas?
Dress for success, not for failure!
An average American 1950s family doing shopping:
An average American 2016 family doing shopping...
Well, never mind!