You've explained this phenomenon to me before, but from what I've recently learned both parties are responsible for adhering to the cycle.

Agreed. The problem is that at the outset often the security source is not completely aware of the dependency. In fact, the security source may initially feel a bit like a hero for being able to soothe his or her companion. It isn't until the patterns are in place for awhile that realization starts to dawn, and then extrication from the pattern becomes difficult.