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Flexibility
The first reason is you can have just the one set of queues on your computer and you are able to print to any of the MFDs on campus; you choose simply by what device you go to and scan your ID to release the print job.
Security
The second reason is secure print release. When you print your job it does not immediately start printing at the printer, it waits for you to go over to the device and tell it to start printing. This way, if you are printing a sensitive document you are at the device to grab the document as soon as it is finished printing (i.e., it is not sitting there waiting until you walk over to the device).
Environment
The third reason is environmental impact. Attached to this article is a document reporting the number of pages saved by using release queues. These are pages that were sent to the queue but were not printed (e.g., person changed their mind about printing, etc.).