Why does he just not care?

My soon to be EX husband and I were together 12 years before he got under investigation for charges that are still underway. I would rather him not see our kids (since was on a underage child within our family), but the state granted him reunification services and he was able to see the kids supervised by the state one hour a week at a public place. He would show sometimes and then skip numerous times. and now has just stopped seeing them all together it has been 4 months now. He called last week out of nowhere and wants to see them on Fathers Day. I told him no. Why does he do this and take everything out on the kids? Does wanting to see them on fathers day give him some sort of gratification of importance or what? Am I wrong to not allow him to see the kids? To me its detrimental, for them to see him for a few weeks at a time then he vanishes for months. He is a soldier so he thinks he can get away with everything, including the , which he has not seen bars yet but hopefully soon. And just because he is a soldier has nothing to do with him not seeing the kids. It was court order and his command had to follow what the court says, but he just refuses to see them.