Suppose you're allocating computer memory to local variables associated with a host of objects (maybe millions). You need to free up that memory when an object is no longer needed. So you need a way to be able to tell whether the memory still has any local variables still in use pointing to it.
This can be visualized as a directed graph. The set of nodes with only outgoing edges are the variables still in use. The nodes with no incoming edges represent the memory no longer in use.
And it appears that at any given moment, the set of nodes with no incoming edges will always form a cycle -- eddies in the directed graph that represents your memory allocation.
For some reason, I find that aesthetically satisfying.