These people are generally not technically knowledgeable at all. If you opened up the phone so it could run any software, all of them would instantly become infested with malware that would massively invade everyone's privacy and probably steal their credit cards and scam them.

I grew up with the open Internet starting in the 1990s. I feel like a lot of people haven't wrapped their heads around just how hostile and riddled with scams and hustler bullshit it's become. The mobile ecosystem is the worst, possibly even more user-hostile than the web. The potential for privacy invasion is a lot higher too since people carry their phones around.

The Internet today is a "dark forest." Any platform made for technically unsophisticated people must be locked down like military hardware for operation in a theater of war. The iPhone is actually not locked down enough to protect most users' privacy.