In most cases, the WAS was a LBS for years prior to walking away. The difference is only a matter of logistics.
As a WAS, it's not our intention to make the LBS miserable, just to make ourselves happy. If the LBS spent the last 5 years living a certain way -- by choice -- then it's reasonable for us to think that that's the way they want to live. It's not our job or even our right try to change someone else so that they'll meet our needs.
If we ask and our spouse obliges, then all is good. If we ask and they refuse, then there's nowhere to go with it.
If the need is critical to our happiness (like intimacy) but you're more interested in hanging out with your buds or work or playing/watching sports, then we feel we have no choice but to look elsewhere. We figure after we leave, you'll continue as you were and not even miss us. I would say that most WAS's don't get the "big deal" made after we leave. Especially in light of the little effort made while we were there.
Even if changes are made, we suspect they're only temporary, because we've already watched as you lived your priorities. You're trying to convince us that you've changed, but the problem is that we've changed, too. You're not addressing the same person anymore, so it might not work to give us what we used to want. Years of what you're going through now -- tears, pleading, confusion, loneliness -- changes you.
What does it take to prevent M's from getting to this point? It's not for lack of M self-help books. It's not the unavailability of counselors. It's not because D simply doesn't happen, with 50% of first M's and 67% of second M's ending that way.
Does nobody ask their current spouse, their life-long partner, "Are you happy with me?"