Halloween: Costumes or Lack There Of

"I'm a mouse, duh."  Everyone that has seen the movie "Mean Girls" knows this quote well.  As Karen walks into a Halloween party wearing nothing but lingerie, someone asks what he costume is.  Pointing to her mouse ears, the only indication that she is wearing a costume, this is her response.  In a movie, a scene like this is considered comical, but recently, this seems to be a reality.  

Walking around on October 30th and 31st, I saw a wide variety of costumes.  Some people "pulled a Karen," wearing barely there clothing that has a small indication of a theme, where-as others went all out in over-covered outfits that really did conceal their identity.  And then, of course, there were those in a happy medium, as well.  For the Karens in the world, I have one question: Why?  What makes you want to leave the house in a complete lack of clothing?  And did no one warn you that it wasn't appropriate?  Don't get me wrong, I understand that it's fun to wear somewhat suggestive costumes (for example, I was in a guy's t-shirt as Tom Cruise from "Risky Business" - not the most modest of costumes but still covered).  

Let me know, am I way off base?  Are my ideas of appropriate that different from others'?