I wrote a longer post about that elsewhere but there is morally no good justification to restrict everyone else's devices just because a small minority falls for scams. This is a very principal issue in a free society and in most societies we allow all kinds of individual risk taking because we believe that adults should make their own choices even if that means that some people sometimes make mistakes.
On a side note, it is technically very feasible to help antivirus and security software makers to lock down phones for people who would benefit from it. For example, you could have a strict whitelisting approach for vulnerable users (e.g. elderly, bitcoin entrepreneurs, annoying kids, Google engineers) who prefer it that way, making installation of arbitrary software impossible. Giving up choices voluntarily is fine, taking away choices by force is not fine.
On a side note, it is technically very feasible to help antivirus and security software makers to lock down phones for people who would benefit from it. For example, you could have a strict whitelisting approach for vulnerable users (e.g. elderly, bitcoin entrepreneurs, annoying kids, Google engineers) who prefer it that way, making installation of arbitrary software impossible. Giving up choices voluntarily is fine, taking away choices by force is not fine.