Thought the Hardy boys, and serials in general, was a rather enlightened reply. Never knew the resistance towards new'ness was as vicious back then, thank you all for the information.
I'd go more with basic psychology though. What defines "cool"? Let's make it more personal, what are the qualities that adhere to a cool person? Is it the jock that surrounds himself with admiring peers and cheerleaders? I'd say that the concept of what is cool is a mutual understanding between individuals, the pack or swarm mentality. The coolest, or most admired / envied, person is the alpha of the pack. Would a person be cool if he had nobody to be "cool" to, after all?
Reading is a solitary action. It's on the large part anti-social behavior, even though I (personally) love discussing what I've read with other people afterwards. But the act itself remains a personal and reclusive event. There's steps you can do to alleviate this fact, a room full of people could listen to an audiobook for instance but let's be honest, how many of us have ever done that (or even -want- to do that)?
Thus, reading cannot be cool since you're not part of a pack when you do it. I'm no psychologist so I might very well be talking out of my behind here, but that's how I've always seen it.