I went to a top 20 university, even higher ranked CS program. There were plenty of weeder courses. There were also plenty of students that were only there to get the piece of paper they believed, probably rightly, was necessary to get the job they wanted. All of the CS courses were recorded, attendance never mandatory for lectures. It was not uncommon at all for lectures to be less than half full due to students watching a months worth of lectures right before exams.