The issue with "why" questions, is that, generally, there is a really easy answer, and a maybe impossible answer. The easy answer with most of these questions is "because that is how it is defined in the JLS". The "why" its that way, ie. the hard answer, would require that it be answered by one of the
Java designers. All that us mortals can do is speculate.
So... Why? Because that is how it is defined in the JLS. Anymore than that would be speculation.
Henry