Some students simply do not know to study properly. The first step to studying is finding the proper place. It is very easy to fall into the trap of studying in your nice warm bed, or on a cushy sofa. Recall is better when study context are similar to the test context. This is a wise decision.
Libraries are, in general, well-lit and quiet.
Another positive aspect of studying in the library is that , in a library, you are not subject to the vast array of distractions that you are subject to if you are studying at home or in your dorm room. There are no telephones ringing. There are no televisions or radios blaring. At home you are subject to televisions, telephones, and family members. In a dorm you are subject to noisy roommates, chatty friends, and noisy neighbors.