Doesn't this argument essentially boil down to "people are stupid and we should take away their freedoms to protect them from themselves"? I'm not going to say that most people would make use of being able to install 3rd party apps, or even that it won't give malware more chances to get people. But people can get themselves hurt or compromise their electronic security in any number of ways taking away people's choices until they can't make bad decisions anymore just doesn't seem worth it to me