Only because it affects the ability to accomplish our shared goals. If we're sitting in an office at keyboards, and you want to wear a suit, go right ahead! A woman in heels in an environment that ought to have steel-toed boots, or a hoodie wearer in an office whose hygiene is so poor that the smell affects those around them, both impact things that are actually important.

But when those personal choices are immaterial, whether choosing to over- or under-dress, they shouldn't affect what I think of others or what others think of me.