Do you think it's weird that Kurumu, Mizore, and Yukari do not wear school uniforms (except for the skirt) everyday?

No,its just how there showing their character,yukari's outfit shows shes a witch,Mizore's shows shes a snow woman,and Kurumu's shows shes a succubus

I don't know. I only see moka with uniform :). I think Mizore looks better without uniform.

i will admit i have always wondered the same thing. i also really don't think Mizore's or Kurumu's outfits signify there monster forms. Yukari's definitly does with the whole witch's hat and cape.
I think Kurumu's outfit is the way it is because due to her umm.. traits it reveals mais of her form where as if she were wearing the standard uniform it would cover and hide her body mais since there is that jaqueta like part of the uniform. Also with Mizore's outfit i personally think that mais so shows off her different personality, almost like she is showing that she is not part of the majority but is her own unique person and her outfit i think says that about her perfectly.
Well that is my best answer for this pergunta but just like the tootsie pop the world may never know.