Reading is Un-comfortable?

Why is it that, as a reporter, I feel perfectly within my rights and completely at ease looking at random web sites on my lunch break (which is always taken at my desk when it's taken at all), but begin to get all ferrety and uncomfortable if I pull out a book instead and read at my desk? Why do I feel self-conscious when that happens? Perhaps it isn't just reporters, or this reporter, who feel this way. And would I feel less twitchy if I pulled out an Amazon Kindle instead of a paperback?