I am not married, but I had two SO's who were directly affected by me using porn. They both knew I used.
To answer your question, I didn't realize or maybe ignored I caused them harm. I had bad ED with both of them, and I thought that it was my problem and not theirs. I was not aware, that this reflected back on them and their self-worth or that they might be really hurt by me looking at pictures or videos of legions of women. Both women told me that btw - but I put it aside, didn't think it was that big of deal (after all, porn is not real live women or cheating - is what I thought).
On top of that, the desensitization from porn negatively affected my feelings and I did not give my best in the relationships, since I diluted and weakened my libido and also my love with porn. My numbness sure hurt them as well.
In short, I was selfish and ignorant.
In hindsight, it was stupid. I started trying to change, once I learned about the negative effects of porn and especially reading the accounts of reboot partners, which made me understand their side a little bit better. But that also came slowly. I started to reboot to help with my P.I.ED and even then it took a few more months for me to realize, that this does not affect me alone (besides from the obvious not being able to have sex).
In the beginning of my reboot, my partner said she hears what I am saying about P.I.ED, but deep down inside her she can't stop thinking she is the issue herself. That she is not attractive and that is the reason, why I don't get turned on by her. And she can't make that nagging voice stop, even though I keep telling her differently. She even said, she wants to try and work on herself, so that she looks like pornstar, so I start to get turned on by her....
She also says, she will very likely leave me if I go back to using porn. I believe her.