There are many reasons why men don't pay and it's not all black and white.
I say that as a single mum for many years who didn't get a penny from my ex despite him seeing them eow.
I could have gone through CSA but he was dreadful with money and I knew it would made him even more stressed and depressed which would in turn impact on his relationship on his kids.
He then became self employed and I knew that getting anything through the CDA would just be a lot of stress for little coming in.
I found it easier and less stressful to budget everything with the certainty of what I earned even if at times, it meant being very right and having to do without some things.
I did it all for my kids and them only. They don't remember the things we missed out on (easily forgetable) but do have the memories of good times with their dad, and to me that was priceless.
As to him, he is the one who has to live with his conscience.