I took it to be a bit of a statement on instant gratification. You expect to visit XKCD and get a dose of humor (or something equally interesting), consuming it

I took it to be a bit of a statement on instant gratification. You expect to visit XKCD and get a dose of humor (or something equally interesting), consuming it in a few seconds before walking away. This strip can be seen as a reminder that some things are worth a longer investment of your time -- though maybe you don't feel that a drawn-out reminder was necessary to drive the point home.