Is it really a mystery that every gesture Hillary Clinton makes is a highly considered and calculated step? As such, it's a pretty safe assumption that PANTS aren't a mistake.
In many ways, Hillary Clinton's interest in PANTS might be the clincher in convincing the American public that she's not really a woman. Or at least she's not SO womanly that she couldn't run the country. Americans are complex people, PANTS indicate a lot to them.
If you're not wearing pants, Americans get upset, if you are they get upset, if you're president you must wear them at all times.
Hillary's reluctance to wear skirts isn't because she doesn't understand fashion or she doesn't LIKE skirts. It doesn't matter what she likes. Does she like anything anyway? She's been a celebrity long enough to more or less lose her capacity for emotion.
It's just that PANTS are a strong indication that while she has a vagina, she can still act like she has a dick. It all comes down to market research.