Most majors are not so structured that one has only one chance in 8 semesters or 12 quarters to take a needed class to graduate within that number of semesters or quarters.
But it probably is common for students to plan their 8 semester or 12 quarter schedules poorly by delaying critical prerequisites so that they put themselves in a position where not getting a particular course in a particular semester or quarter will delay graduation.
Students may also end up in that position if they were late in deciding a major, or changed majors late, so they have to cram a lot of “catch up” courses into their schedules.
There are also students who take lighter full time loads (12-13 credit units instead of 15-16 credit units) because of work or family needs.