Nerds don't just happen to dress informally. They do it too consistently. Consciously or not, they dress informally as a prophylactic measure against stupidity.
Dressing up is inevitably a substitute for good ideas. It is no coincidence that technically inept business types are known as "suits."
For [a product] to surprise me, it must be satisfying expectations I didn't know I had. No focus group is going to discover those. Only a great designer can.