I've seen and experienced enough situations to where it's almost impossible to surprise me.
My conclusion is that in most cases neither side of that relationship cares. They're in the "situationship" their in bc their both getting a specific thing. And often that thing has little to do with commitment or loyalty and more to do with the physical things of life.
Rarely, but in some cases, a person really doesn't know and on course for some major disappointment and pain. In those instances it pains me a bit, especially when their are children involved.
But not to the point where I'm going to get involved.