Well, ultraviolet is a whole other realm... we are just dealing with visible light here, as thats all standard cameras can capture, and 3D programs only mimic standard cameras... they don't even typically mimic the human eye... just cameras.
Moving on, nothing really bounces more light it recieves, rather, in some instances surfaces can create light of its own via various processes which are catalyzed by light itself.
That site explains how black-lights work... the surfafces being struck are not bouncing more light than they recieve, rather, various phosphors coating the surface react to the light as it strikes them, and these phosphors emit light on their own.
The real world is a much more complex place than it might initially seem ; )
DGS was not designed to simulate extra surface attributes like phosphors and such, rather just to simulate how a light source will affect the surface it is striking...
But, in the end, there is no way that anything in the CG realm will 100% replicate the real world, as the real world is far too complex...
DGS does a damned good job of simulating the most simple lighting scenarios...
phosphors and other factors aside : P
p.s. yes, DGS is off for "many surfaces" and doesn't do "lots of things you and me see every day" but its just specialized for the more common conditions...
Thats why there are other shaders, like dialectric, which handles more specialized "light passing through transmissive media" situations.
There is no "be-all, end-all" shader, DGS just works very well for many common situations, as it was designed to do.
As a side note, if anyone wants to design a Mental Ray UV Light shader and a phosphor simulating shader, that would be quite a project ; )