Honestly? Because she's not very smart..

and I don't mean to be.. Mean but she doesn't know the difference between 1/2 cup and a 1/4th cup. She thought
ducks were asexual, doesn't know the difference between horizontal and vertical... Told my 5 year old she can't help her with homework because she doesn't know what nouns are.
She even got pissed at me because on my taxes I'm claiming married but higher single rate because I thought the divorce would be over and I didn't want to claim married and then owe the IRS a ton of money. She said I only did it to make my checks lower to get rid of child support... I've explained numerous times that's not how it works but she says "no you're a liar and trying to get out of supporting your kids".
Fortunately for me the guardian even said " Mrs ********* is clearly not as intelligent as Mr. ********" to the judge (he said this behind closed doors infront of both lawyers and mine told me he said this" so I get to make 100% of all medical decisions.. But she gets to pick schools because she's the majority parent.. Ugh