I've been emailing with a student while I was away; this student doesn't have the courses he needs for next semester, and is complaining that his advisor hasn't helped him get into the courses.
I don't know what the advisor has or hasn't been doing, but unless it's the advisor's own course, she doesn't have a magic button to press to put the student into a class that's already full. We don't just overload other instructors' courses (though the deans have already raised our enrollment caps again).
I know that frustrates students. But there's a cost to overloading, not just in terms of an instructor's workload, but in terms of how a course works. It may seem like nothing to add one student to a 20 student course, but we're already raising enrollments, and there's a large supply of students who'd want to overload in, not realizing that a writing course with 30 students doesn't work nearly as well as one with 20 students.
I don't know why this student didn't enroll during the primary enrollment period, but I'm pretty sure the courses he's complaining about had spaces then. (Though, yes, of course, that would have meant a different student might be emailing me, or just feeling frustrated all alone.)
When I was an undergrad, we had the same problem with students not always being able to get into the courses they needed. People who could afford to put a downpayment on their registration fees got to put in their class choices earlier than those who couldn't. For me, that meant I usually got the courses I needed when I needed them. My friends on financial aid didn't always have that good fortune, and so didn't always get their courses. That meant it took longer for them to finish sometimes. NWU recently implemented a policy to holdover the downpayment from the first semester so that it could apply to all the semesters (or something; I'm not quite sure how it works), so at least that's not supposed to be a problem now.
I wonder if there's ever been a public university that actually had enough seats for all its students to take the courses they wanted/needed to take when they wanted/needed to take them?