(for the post's preservation's sake)
Now that I have quite a few raw cakes, I can offer input as to why most people will keep their cakes intact. It's all about asthetics.
Unlike a jar full of loose tea, a raw puerh cake is like a pet of mine; the opposite of a pet plant, in that it never grows and will eventually disappear if I give it too much attention.
Another reason is that I find the delicate maneuver of prying a piece from one of my cakes (or even individual stem-leaf systems from "wild-tree" cakes) can greatly add to the overall therapeutic value of drinking puerh; I guess it's a form of foreplay for tea drinking?
P.S. Something that I think goes unspoken, and I could be wrong, but my results have shown me to be correct; the reason to be careful about prying apart a cake is that a whole leaf will provide better flavor and have less of a chance of becoming bitter after a few brews, as compared to having several of the leaves broken into pieces.