Because the woman is a national treasure. There's art just in the way she holds her chin.
Something I noticed for the first time: look at her suit from His Girl Friday. See how the seams on the sleeve are meticulously aligned with the seams at the hip so the geometric pattern is perfectly uninterrupted? Damn. Interesting that, while Russell wears only two suits in this movie, both are so stripe-intensive. It's from Kalloch, who evidently knew what stripes can do for a woman. And who was, obviously, a genius.