The reason I ask this is that c# could easily have copied the java convention, or a variation of it, but opted for the more flexible approach of explicitly declaring namespaces inside files. As a Java programmer often there are things that I wish I could do differently, but namespaces is not one of them.
The flexbility has a certain overhead (extra braces, extra decisions for developers, making it harder to view a projects contributions to the namespace, at least without a specialist IDE). So what practical examples are there when this flexiblity is advantageous?