From what I understand, there are two things at play here.
- Certain rules / criteria must be met in order for a developer to have their stuff placed on the marketplace (prime example the A32NX being pulled from marketplace and XBOX)
- For all the other “add ons” that PC users benefit from, the XBOX is a closed, encrypted system. Folks like VATSIM have already stated they will not (for the time being) be venturing down the XBOX route for these reasons. Air Manager, Etc… All in the same boat.