[nirui]

Sometimes hiding internals is reasonable, but it could cause inconvenient. Exposing everything could make it harder to do interface management etc.

It's really a system design problem rather than access control: if you separate functional modules in a reasonable way, then it can be better reused.

[magicalhippo]

Only if you use a backwards language with non-existing namespaces. I don't see how it changes anything if you have namespaces. After all, private/protected/public are just namespaces, they are just implicit rather than explicit.