Why do people stand still on an escalator that's going down?

Sometimes, when I go to the store, I need to go down a floor so I walk over to the escalator, step on, and continue walking down the escalator. Usually, about half way down, I have to stop because someone is just standing there blocking me and there's not enough room to go around them. Could these people BE any lazier?  How about a little courtesy please?  It's really not much harder to walk down the escalator than it is to stand still ON the escalator (and it's quicker). I can see standing still on the up escalator because it takes quite a bit of effort to walk up stairs, but not on an escalator that is going down.