Correct. It's not practical because those apps usually aren't Free Software and because the hardware or firmware they're running on often aren't Free and includ

Correct. It's not practical because those apps usually aren't Free Software and because the hardware or firmware they're running on often aren't Free and include anti-features that prevent you from installing Free alternatives. If they were Free, users wouldn't necessarily even need to hire a developer to change their app or OS; those changes would most likely already exist in some form somewhere and the user could simply purchase the modified version.