Why does my BD act like this?

Why is the father of my kids arguing with me constantly about wanting to see his kids, his rights and how much he loves them as if I'm keeping them from him (which I'm not) but he still doesn't put in the effort or try to visit them or spend time with them? He has seen them once in the last 3 months for 1 hour. He gets paid a fair amount of $$ weekly and doesn't even consider using it on his kids but is quick to brag and show off his wallet to our mutual friends and tells them he "wants" to take our kids shopping but I won't let him 🙄 he couldn't even buy our daughter at least 1 birthday present last month. I'm so annoyed with this guy, he will have the time to message me daily just to argue but never mentions the kids or asks how they are for the most part of the texts, he is very manipulative and I'm sure there's a touch of Narcissistic traits he carries. I just can't wrap my head around the way he is and it's so hard to try and understand him when he thinks as long as he blames me there's isn't a thing wrong that his doing.