Nobody else would bother. That’s why meme language repositories continuously lead to hacks and vulnerabilities.

Which is exactly as it should be

I actually don't have (much) of an issue with walled garden approaches as long as the wall has a gate that is easily opened, give me an OS level toggle with a warning of "Here be dragons" and I can live with it - it's not ideal but it's not a terrible trade off.

It's something Android has had previously (but they seem to be trying to lock that gate) and iOS less so.

We also can't count on every person being able to check every single thing they do: how do you check if some food or drug you get is good or not? you can't really, you have to trust someone who knows.

A phone/tablet is a tool, with very intense usage, and huge privacy value, not an engineer's toy.

Microsoft will upload these executables to the cloud by default if you use their antivirus engine ("sample collection").

In a way, Microsoft is building the same "notarisarion database", but it's doing so after executables have been released rather than before it. Many vendors and developers will likely add their executables to that "database" by simply running it on a test system.

On the other hand, SmartScreen can be disabled pretty easily, whereas macOS doesn't offer a button to disable notarisarion.

In practice though they use it to turn the screws on various API compliance topics, and I'm not sure how effective it is realistically in terms of preventing malware exploits.