It is the other way around. The security model of mobile devices seriously inhibits innovation and we end up with ever the same crappy apps we don't really need.
I also don't believe more people get scammed on PC compared to mobile platforms. Scammers go where the most naive people congregate.
A sensibly configured Linux system is very secure compared to your mobile device. No security model can really shield against user stupidity. The people would need completely different devices as they simply aren't fit to use a computer. My parents are the same, but I won't accept a bad compromise of an OS just because they essentially need other devices.
At some point a user will be asked to allow execution of code they got through some fishy mail. There is no defense against that other than for the user sticking to books.
>A sensibly configured [desktop, i.e., not just a headless server] Linux system is very secure compared to your mobile device.
That is not true. It is understandable that you believe it because it gets repeated a lot, but those repeaters are doing what you are, namely repeating what they heard (and sometimes what they want to be true) without sufficient actual knowledge of what they are talking about.