Simple supply and demand is the leading cause why students arent able to get their books if they try later rather than sooner. Also, students frequently dont know that the bookstore has a very small window available to sell the books back to the publisher for a refund themselves. The books on the shelfs are inventory and have a price to be payed just for having them sit there, so the bookstore will sell them back after a few weeks into the term, once all students had a fair chance to buy. Lastly, books change very frequently from term to term for classes so there is no point in the bookstore keeping books that very well could be updated in a few months and seldomly bought after the first few weeks of the term anyways.
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