But then I think, this is true of all of us and no-one is ever 100% fixed so we have compassion and learn to live with each others' baggage. The issue for us BS's is the fear that they will repeat their behaviour.
Nice post Katie!
Bottom line is, people cope. Often they cope badly. Your H, mchercheur, sounds a lot like mine. I used to use the word oblivious a lot too, but now I use the word denial. My H is very comfortable using the coping skill of denial. TBH, it's not an entirely bad skill, in the short term, but too often it's insufficient for the long term, and repressed feelings can resurface at the worst times culminating in bad behaviors like infidelity.
I firmly believe that a WS should face their "why". I also firmly believe that a BS cannot force them to do it. However, I also eventually came to believe that some waywards will never truly face their why. Here is the answer to your question: It's just too painful. They might be able to come up with a general idea of their why, but the deepest darkest pain inside them may never be dealt with completely. Therapy might help, if they were willing to go, but again "you can lead a horse to water....".
I understand how frustrated you feel. Been there, got stuck there, done that. It wasn't until I was able to let go of hoping he could change that I was able to move forward. I had to accept that this is who he is and I could love him that way, drive myself crazy, or leave.
I also realized that my H could supposedly "fix" this thing about him, but it still didn't guarantee he wouldn't cheat again. Nothing (except maybe death) could guarantee that.
Now, I guess you could say that I settled. For years it sure seemed like I was settling (but this was my issue). But really, although my H did not do all that I asked, after his infidelity, he did do many good and necessary things to calm my fears. I had to decide it was enough and love him as is. So that's what I have done. And we are happy.
I recommend a book called "Healing the Shame That Binds You" by John Bradshaw. It's about toxic shame, which may be your H's issue. You may not be able to get your H to read it, but it may help you understand him better.