Cause when I'm at Disney waiting in line for a ride or bus, its easier to carry, lighter and I can put it in a ziplock bag that holds the reader, cellphone and wallet if it rains. All while fitting in a cargo pocket of my pants/shorts. Oh, and it works for days and only needs a usb cable to charge, like the one on my cell phone. Netbook/laptop means an extra PSU. Works better on the airplane as well.