I've always been interested in fashion. Aware of clothes that looked good on others and why, yet, I never dressed particularly well myself. Until the day that the boss at my first job berated me via e-mail for my poor style and grooming habits.
I was mortified. Angry. Ashamed. And I called in sick the next day and went shopping for new clothes.
Ever since, I have been incredibly conscious of my appearance. And while looking back at that experience remains slightly traumatic, I am grateful for that wake-up call to superficiality. It was a reminder that dressing up isn't for you. It's for others.
If you don't care what people think of the way you dress, you should. Simply because of how powerful our blink judgments are. You are judged based on your appearance. You are treated differently based on your appearance. Your perceived intelligence is weighted based on your appearance. Whether you believe in the moral rightness of the fact doesn't change that fact.