It's not that I choose to read in the bathroom, I just don't put my book down unless I have no alternative (and even if I'm not holding it I'm still reading, particularly now I've got a tuff-luv case with a stand for my reader).
I have an aquapac for my reader, but I also have a technique for reading pbooks in the shower.
Entering the bathroom just isn't a reason to stop reading.
Both I and my mum can remember as children reading the labels on all the cleaning products in the bathroom when we weren't allowed to take books with us.
Sometimes I do listen to the radio instead - also have a waterproof radio