“TI’s calculator ecosystem facilitated a needed educational reform and created training resources for math teachers. Its emergence as a national standard simplified math education, reduced teacher training costs, and contributed to teacher job mobility. Educators, who may have taught for decades, even preferred the lack of innovation. Additionally, students have been able to take standardized tests and enroll in STEM courses in college without needing to switch calculators.”
https://www.promarket.org/2024/04/08/tis-calculator-monopoly...
(Also, TI supports RPN. It also supports PN and infix notation.)