They were dying long before smartphones. Cheap Casio calculators happened. I have a little $15 Casio scientific calculator and it has been all that I've neede

They were dying long before smartphones. Cheap Casio calculators happened. I have a little $15 Casio scientific calculator and it has been all that I've needed for college and professional work. But it can take integrals, derivatives and has a general newtonian solver. It covers everything except matrices. Those are miserable to do on any calculator so I'm not missing much. In all my life I've only ever seen two HP RPN calculators. One belonged to my high-school chem teacher, the other to a real estate agent. If there were a $30 RPN calculator with similar functions, I would use it. Edit: 18 years later and they still make it, https://www.casio.com/products/calculators/fraction-and-scientific/fx-115msplus https://www.casio.com/products/calculators/fraction-and-scie... Edit2: Looks like the most readily available RPN calculators are the HP 35S ($55) and HP 12C ($50).