Concealment of Japanese Book Covers

Why do people in Japan conceal book covers when they read? Perhaps this is why most of the book covers are so utilitarian-- not much but the title with a one color background. Book covers in the U.S are more sophisticated, colorful, graphic, and sometimes persuasive. It's because they don't conceal them! But why is it so ordinary that Japanese people conceal them? The covers don't seem to be embarrassing--unless you're reading an X-rated book--especially since most of them have nothing but the title and the author. Is it because they don't want other people to judge from what they're reading? Are they afraid that they are reading a bad book? Are they not confident enough to show the public what they're reading? Wouldn't other people be more curious in what they're reading and ask them more often?

I mean, think of it the other way. In Onsen (public bath), people bathe together without minding their privacy. Perhaps one could argue that it's because people are all the same and there is nothing new. But still, it's ironic that they don't mind being in a public bath nude and actually do mind about showing what they read.

Not only do Japanese people conceal books, also when they eat. Now I'm not saying ALL of them do, but some of them. This might be because they don't want other people to judge from what they eat; some might think it's disgusting. But still... y'know? It would make sense if they were eating something very esoteric such as natto in the middle of the street in New York, but not in Japan, since most know what it is.