I have a case for a few reasons. The protection issue is one. To prevent accidental button presses (i.e. turning on, page turns etc).
My cover makes it eaiser to hold (feels more like a book) and looks kinda stylish too. Also it camoflages it from my 3 year old who will pick up and play with anything that has a screen in it (he thinks its a book and daddy books are dull)