I think it has something to do with the fact that I have never seen a TI calc with a RPN mode, while many HP calcs either make RPN the only or the default mode of operation. And since engineers love RPN for reasons mentioned earlier in the thread... That's probably also why I've never seen an HP calc in-person throughout my high school years. Always TI-83s/84s, the occasional student-owned TI-89, and a few odd cases of TI-85s/86s. Algebraic/infix notation is what they teach, so it's probably more natural for people to just punch in those formulas verbatim rather than trying to make them fit into RPN somehow. That, and for whatever reason, the public school system seems to decree the TI-83/84 standard.