Why do some people at fast food restaurants fail to form a line, and just hover around far back?

Sometimes I’ll go into McDonald’s to get my coffee, and I’ll walk straight up behind the guy whose ordering. Then I realize there’s a bunch of dummies in the back who are also waiting, but haven’t ordered yet. (They’re waiting in the same area as the people who’ve already ordered).

Why didn’t they form a line? Does this seem to happen more often now?

And is it proper… perhaps even good… to cut right in front of these people for behaving illogically? Almost always, they don’t say anything…