The other thing about room only is the cancellation policies are much more lenient than packages - with a room only you can cancel and get your deposit back if you do it less than 6 days prior to arrival. With a package there is a cancellation fee of $100 if you cancel between 45 and 6 days out, and $200 if you cancel within 5 days of arrival.
However, if you decide later you want a dining plan or something like that, you can't just switch a room only reservation to a package, it needs to be cancelled and rebooked.