a) As a programmer, I'm not being hired for my appearance, but for my ability to get stuff done and create value.
b) I can get far more work done and think more clearly when I'm comfortable.
c) If you have a problem with somebody wearing jeans and a t-shirt or gasp, even shorts in the summertime, that's on you, not on me.
On the rare occasion I've ever had to go to a job interview, I've ranged from shorts/jeans to business casual at most and have never felt out of place.
If you want to play dress up for a living, go become a lawyer or model or real estate agent or some other profession where you're constantly judged on how "professional" your appearance is. That's not what programmers are usually about or motivated by.
So what you wear is completely irrelevant? Or does Martha Stewart a better security analyst than Bruce Schneier? With no disrespect intended to Dr. Schneier, she certainly has better decor, food on the table, and scents in the air.