For a lot of people it does help the, um, process along to have reading material, to occupy the mind while the body does its thing. I don't think it's really a physical necessity, more of a psychological/habitual thing. When I smoked, I absolutely had to have a cigarette while talking on the phone ... same sort of connection.
Until I saw that "Seinfeld" episode, though, it never occurred to me that my bathroom reading material might have cooties. Yes, I've read the studies that say flushing spreads toilet germs throughout the room, but if I'm able to put my toothbrush in my mouth without getting sick, I don't worry too much about what random germs might be on a book or magazine that went into the little room with me.