>>Camper+ff
It’s a security boundary. It lets you control the resources an application has access to. For example, if that cool weather app you just installed asks for access to your Documents directory, or your camera or microphone, you can say no.
>>pauldd+vI1
Visiting a website and running Javascript vs. running a native application aren't equivalent. Browser sandbox exploits are "a thing" but that doesn't make the situations the same.