You would think so, but there are enough people who screw this up (either through their own fault or because of circumstances outside of their control) that 5- and 6-year graduation rates are things that colleges measure.
What they usually mean is that some required classes are not available every semester or every year. This trips up some students if they take a non-standard path through a major, usually by changing majors late in their academic careers. Calling it ‘extortion’ is a little much; the issue is that not all universities can offer every class every semester. It costs a lot to offer a class and if only a handful of people need it there might not be staff or space available for it.