Have you ever worked with someone who barely knows how to use a mobile phone? They will hand their phone over to someone they barely even know to do something they don't understand. They will follow instructions from a stranger over the phone, without understanding what the phone is warning them about.
I have worked with such a person. They did have someone walk them through a dubious process. Thankfully they realized what was going on before the process was complete, but who knows how much damage was done by the initial steps.
There are legitimate security reasons here. Whether there are reasons beyond that is an open question.
Which incidentally is often just a pretense for other motives?
If computers have suddenly become so dangerous for normal people, and they want smartphones nonetheless, add to them a dumb-mode encouraged at the initial setup, and requiring some third party assistance to turn it off once enabled..! (and forbid apps to change their behavior if it's not enabled)
We could also imagine a 24h delay to get Play Store access with a modal to make them understand the risks.