There are plenty of open source replacements for graphing data that involve computers. The calculator is a form-factor challenge and marketing challenge. Calculator markets are driven very early by what is acceptable for a High School Student to use.

Current US influential standards:

http://sat.collegeboard.org/register/calculator-policy http://www.actstudent.org/faq/calculator.html https://apstudent.collegeboard.org/apcourse/ap-calculus-ab/c...