While the author has a point that calculators are essentially pointless (if not downright scammy) these day, I know more than a few people learned to program on their HP calculators. It was my first experience learning the ins and outs of an entire API, eventually deciding it wasn't sufficient and then digging deeper into the previously hidden world of the firmware below and eventually to the CPU itself. Of course you can do that on any device, but it was helpful be able to play around in class without suspicion.