Actually we don't. You're missing the point.
As this thread demonstrates, many medical school applicants have very little sense of style. They struggle with what fabric and cuts are appropriate, what matches and/or coordinates, what accessories to choose and how to present the most flattering, professional and confident facade. For many, its their first time wearing something other than a hoodie and jeans.
Thus the standard "uniform" is safe, comfortable and allows them to focus on themselves and their application. Just like in the men's interview clothing thread, our recommendations are meant to provide a foundation for those who really have no idea.
However (and here is where I think you're missing it), all of us who regularly give advice in here (
@gyngyn ,
@DokterMom ) have said previously that we would be thrilled to see someone in something other than a black suit with a white button front shirt, pearl studs and strand. We've even mentioned sheath dresses with blazers as wonderful; some chunky jewelry, a scarf etc -- IF you can pull it off.
So its not against the rules to wear a coordinating (as opposed to matching) outfit but it is less formal and it can take a sense of style and confidence to stand out that many applicants don't possess. An attractive candidate wearing a camel wool sheath with matching coat, tortoiseshell jewelry and a warm cognac bag and shoes with a strong application? That superstar will be remembered in a positive fashion; her style will enhance her application. What usually happens is the attractive candidate wearing a short red dress, with a tight black jacket and high platform pumps and possessing an average application. Her style detracts from her application and makes her "that girl".
Lastly, our concern is that an applicant who wears something considered inappropriate/ill-fitting/unfinished etc doesn't understand what passes for business professional in OUR world (or chooses to ignore it) and that opens you up to more criticism of your application. Hence, the "safe" recommendations.