It's an option, and it sure is neater to those
creating the library, but it's much less neater to
those using it. Not everyone compiles a PHPDoc for themselves when downloading a library, so then all classes form a nice big pile at the root namespace.
In terms of neatness and ease of use, I choose like I'd choose how to optimize code - I focus on the parts that get most use. Users of a library are hopefully way more than its maintainers, so it feels like it's worth slightly inconveniencing the maintainers in order to have an instantly clear public interface.
