Maybe your university is small, i have a lot of classes with about 150 students. There are always not enough textbooks for that number of people. I find hard to believe a library is going to purchase more than 50 copies of one book title.
Which is why they are on reserve. Essentially reserve only allows you to have a textbook for 2 hours and there are usually conditions which do not allow you to reserve it more than x times per week etc.
If there are 3 reserve texts for a 150 person class where likely 80% of the people in the class own the book/are not aware of the reference section, you can assume that you will be able to get a book reserved for a few hours at your leisure (or at least get on the waitlist).
Neither my college or department library had a reserve system.
The department wouldn't let you take key textbooks out of the library, but you could easily squirrel one away in a corner and work for days uninterrupted.
