I have been wondering why I bother as well. I think we can only take so much and our psyche switches to protect us by going numb (also called detaching?)
When I started nc, it was hard not to reply to H's negative emails but after a week it suddenly got easier and I couldn't care less anymore. All this DBing... what's the point if H feels it's not worth it to work at M. This nc is going on for almost 1.5 mths and it's totally dead. I didn't even contact him for his BD, he always took me for granted and I knew he expected to hear from me no matter how terrible his words were. So I ignored it all.
What he values or not is not my issue anymore. It is not the end of my life and if he thinks walking away fixes his problems, then he can take how ever long to find out he will have the same wall coming up against him again sooner or later.
I culled his side on my FB as on Nfeed I saw his fam writing to a relative "all is fine here, everyone's well". It's as if I've never existed and it feels as if this whole M never happened... did I imagine it all?
If you don't feel motivated to reply, you can hold it until you feel like it. At least that's something you have control over.