Isn't scope just a way to organize classes, preventing outside code from accessing certain things you don't want accessed?

More specifically, is there any functional gain to having public, protected, or private-scoped methods? Is there any advantage to classifying method/property scope rather than to, say, just public-ize everything?

My presumption says no simply because, in binary code, there is no sense of scope (other than r/w/e, which isn't really scope at all, but rather global permissions for a block of memory). Is this correct?

What about in languages like Java and C#[.NET]?