Not because they mean to, of course, but just because they do stuff that doesn't work in college contexts.
I started a class by asking for questions about the reading. A student raised hir hand and said, "I thought the reading was repetitive."
What do I say to that? It's not a question, and it reveals a depth of unawareness; does zie think I assigned it to bore hir and not because I thought it might be useful? (I dealt with it badly, I must admit, because I wasn't prepared for a "it's boring" sort of statement right off.)
Another student came up in the moment I was starting class, stood in front of the whole class (but only talking to me), and told me that zie'd done the assignment wrong. I always wonder what the question is, because it's not like I'm going to redo the assignment for hir, or suddenly say, it's okay, you don't need to do any assignments for the class! You get an A for just appearing! But yes, I know it's because it's the first assignment due, and zie is anxious.
And finally, the number of students who tried to turn in handwritten work (the syllabus states that work must be typed). (No, I'm not impressed that you quickly wrote this during class discussion.)
All innocent first year student stuff, but in whole, it sort of makes me crazy.
I've come to think that one of the hardest parts about teaching is that just when students get really good at it, they graduate, and we get a whole new bunch who are anxious, confused, and yes, first years.