A few reasons:
GeoGebra encourages collaboration
- Limited to the Algebra and Geometry math streams.
- Learner training time.
- Multiple interactive geometry competitors (49 according to the most recent count on Wikipedia.) (Retrieved: https://en.wikipedia.org/wiki/List_of_interactive_geometry_software)
- Although free to education users, commercial users pay a fee.
- Viability relies on commercial fees and grants to continue development.
- Availability of technology required to run the program.
- No hot-line tech support
- Sign in required. May need school board approval to participate.