Shprintze: The “Where-in-the-torah-does-it-say” attitude will get you nowhere. Did you expect the Torah to list every detail of untznius clothing? Do you want a malach to come and tell you exactly WHY you can’t wear pants, sleeveless dresses etc.?
IMHO, tznius is a sensitivity and a maturity. It’s when you understand what we’re doing to the men and bochrim out there.
I wish I were at that point. In the meanwhile, I’m working hard to get there.
Hatzlacha rabba.