Well, the locked-down nature of iOS and Chrome OS are what make them markedly more secure than a general purpose computer in the face of real-world threats. Just this week, my Mom's Chromebook kept her safe from what appears to have been a targeted attack (someone sent her an email with a link to a malicious .ru domain and my name in the From header). That locked-down design is also why I'm writing this response on a Chromebook.

It's for good reason that Tech Solidarity and other security-conscious organizations recommend using iOS and Chromebooks where possible: https://techsolidarity.org/resources/basic_security.htm

Of course, we must fight tooth and nail against any regulations that would restrict access to general-purpose computing, or put limits on connecting a general-purpose computer to the Internet. But it's important to remember that there are absolutely legitimate reasons to use and recommend locked-down machines, and that the most technically adept of us will use a combination of both categories of computing device in our lives.