Your logic states that because an app can occasionally slip through the review process, that we should remove -all- protections. That isn't better, that's worse.
A scam is also a relatively low bar to set for such drastic change, since scams also frequently occur over chat apps and the kinds of access that side-loading and 3rd party stores can avail opens the door to significantly more sophisticated malware. If you truly think the situation right now is bad, just wait until there are no protections for users.
You should also recognise that there is actual data for malware on these platforms. Every year Nokia drive home the same point for why Android has such an outsized share of malware: "...most smartphone malware is distributed as trojanized applications and since Android users can load application from just about anywhere, it’s much easier to trick them into installing applications that are infected with malware."
Since all experts point to the same sources of malware - perhaps that's not the change we should be legislating. How about we do something different.