Why is the meat closer to the bones tastes better?
This contains a nice explanation of why meat is juicy and tasty, and it is due to the presence of fat and conjunctive tissue in the muscles, as well as brining and marinating.

If you take a look at bird anatomy, the chest and other major muscle masses have less fat and conjunctive tissue as they evolved to be, well, muscle masses for propelling the bird around. 

The muscles "closer to the bone" have the conjunctive tissue that connects them to the correlated bone, and in certain parts, the muscles are smaller due to the need for fine movements (like the wings).

I explained in another answer the mechanics of maximizing marinade power, and one of the factors involved is the surface-to-volume ratio of the part you're trying to marinade, which is also better closer to the bone (including cavities)