Well, you're right of course, but I don't think people asking questions on this thread were looking for ways to express their individuality, but rather just find nice looking clothes that show respect and yet are comfortable and reasonably fashionable. I mean, if you take "conservative" too seriously then we all will look either like mobsters, as someone said, or else like we just walked out of a 1970s Sear's catalog, and that's no good either. I think it is perfectly fair to question whether a black suit is necessary. There are lots of nice looking, conservative-enough interview clothes out there that people might debate over this or that thing and still be within the range of what's ok. And as far as interviewers being older men, fine, but you could also say that many older men actually resent women who wear power suits, and instead would prefer the flowery skirt. I mean, people can psych themselves out in many ways if they think about this too much.
Yeah, sandles would be extreme; so would a weird hairstyle or miniskirt or whatever. But then when people start talking about there being some "norm" for what must be worn, well that's extreme too. Doctors need to show that while they can fit in perfectly fine, they can also do more than just tow the party line every minute of every day. Plus people tend to look awkward in clothes that they hate. (That is why I will never wear Easy Striders). There's enough variety among the *appropriate* kinds of clothes to please everyone, I'd say.
I think the people who really deviate from this and draw attention to themselves through their clothes on interview day are in the minority. I don't think it's nice to make fun of them. Most people want to fit in and look right; those who don't might be very inexperienced, or they might not have gotten very good advice. The polite thing to do is downplay the extent to which such people stand out.