He doesn't ignore that "people lose the desire for the relationship to last," it sounds like that's exactly what he's saying the "scar tissue" causes: "and then somebody decides they just don't care anymore," as he puts it.
Some relationships aren't meant to last. You're not likely going to have a lasting relationship with the contractor who built your home. Or the lawyer that represented you in some real estate transaction.
One of the reasons relationships wear out is that you can't have so many well-maintained relationships because there is not enough time to maintain them all. Some have to fall by the wayside, or you have to find a way to maintain them with much less frequent contact than when the relationships were fresh.
At the end of the day your longest-lasting relationships will be with the people nearest to you. Parents, siblings, spouses, children, close friends. All the others are at risk merely because you can't give them enough time (and they can't give you enough time). You can make some number of non-core relationships last, but you really have to choose to, and the choice has to be mutual.
My point that this "scar tissue" only formed because he had no desire to prolong the relationship with the contractor. Imagine a good friend was doing the work instead of a random contractor. Do you think he'd greet his friend every morning by going over every single thing that was done imperfectly the day prior?
That sort of behavior happens often in marriages. The "accounting of flaws" there isn't the first sort of "scar tissue", it's something that happens after a bunch has built up. It then layers up and makes it progressively harder and harder to repair the relationship.
