What is she expected to wear? Frilly dresses? I understand why she wears coordinated pantsuits. Just pick one out of the closet and it’s all there together - pants/top/coat. I dress coordinated too, not all pant suits, but a coordinated set on one hanger. Put it on and you are done, no decisions to make as you made them when you put the set together.
When I worked, I needed to have clothes on (people frown on no clothes), so I could quickly choose a clothing group put together on one hanger, might be a pantsuit or not but it was fast to get dressed.
This type of dressing has a connection with being smart and concentrating on solving problems, not dressing. Albert Einstein also dressed like this. He had numerous suits just alike and shirts just alike and shoes just alike and socks just alike. He could reach in the closet and get a suit and shirt and shoes and socks and dress quickly. His choice of suits and shirts and shoes was made one time when he bought them and then he didn’t have to spend time on dressing as they were all alike.
Engineers tend to dress like this, especially if they live alone. Clothes are not important but solving problems is, so they tend to have simple clothes that go together and socks that are alike so they don’t have to spend time sorting socks.
Another reason Hillary wears pantsuits is, she has a large abdominal/hip/thigh area and the jacket of the suit is long enough to cover all that area so it’s not so obvious she is large in that area. You can still tell it, but it’s less obvious than wearing separate pieces. Also, wearing the same color from top to bottom, makes a long line that takes the eyes of the observer straight down without observing so much the largeness of that area.
Good points, IMO. She found a style that works for her so she probably had them made up in every color, and she doesn’t have to worry about what to put on.