I was a little surprised that Amazon's site doesn't specify a doctype, and is rendered in quirks mode. What could possibly be the reason for this? I understand what quirks mode is and why doctypes were introduced, but I can't understand why this would be intentionally left off.

I guess it might simplify markup if they're trying to support ancient browsers, but isn't that like shooting yourself in the foot when it comes to modern browsers, especially when their site is so Javascript rich? Does this level the playing field when it comes to supporting really old browsers?

Is there something else I'm missing?