Probably because what most people call "love" is really just the first stage of it, and if it has not been replaced by something deeper (i.e. respect) by the time the initial love fades, then it wasn't love but infatuation - or, more precisely passion was not nurtured carefully enough to become respect, and so it was just an infatuation.
In short, it would be absurd to mix up infatuation with love.
Sometimes. The entire problem is that the infatuation stage just doesn't last that long, which of course makes one ask...why did you get married too soon?
The bigger problem as I've seen over the years with people is that they confuse the two with -other- people. A person married for 5 years becomes infatuated with someone else, which of course means they love them and not their spouse anymore. In their eyes, at least. And the problem with that thinking should be immediately apparent.
It's a complicated subject and I'm not an expert by any means, just sharing my observations.
Presumably this could be sussed out long before marriage. And if that deeper love and respect should disintegrate, there would be some sort of catalyst.
My expectation is that it's unlikely in the long-run to fall out of love if both parties still nurture the relationship and invest themselves. But maybe I'm wrong and it happens anyway.
Because that's reacting in surprise to an expected inevitable thing (infatuation fading), and presumably afterwards trying again with a different partner with an unrealistic expectation that in those relationships they might permanently stay "in love" i.e. the infatuated feeling of falling in love, which is quite distinct from long term relationships that we call "love" but IMHO don't apply the label of "fallen in love" anymore.
In this case, if reality doesn't meet expectations, then divorcing just to try the same thing again to get the same result is absurd insanity, instead the expectations should be adjusted.
