[SapphireSun]

Don't knock paper too hard. While it's not so good for networked communications, it's awesome for displaying static information, tearing apart, and drawing on with incredible ease (e.g. when you need a picture, text, or information circled in addition to what's printed). It's also very cheap even if it's not free. Paper is also extremely high bandwidth - no waiting to view it. Flipping through a book yields a higher dpi and throughput than the fastest computer displays.

This is not to say that paper is superior for all the uses of a boarding pass, but it's very hard to displace something so usable and accessible to people without smartphones.