No real reason, my father is basically just a very bad person who liked to rule with an iron fist. My brother, stepmother and I were basically servants to his every wanton need, and even then he would pick faults with whatever we done and punish us mercilessly for them. He spent 10 years in prison and was released when I was like 11, and my mum raised my brother and I until then but she was an alcoholic so he SOMEHOW (despite having done 10 years in prison and only been out a matter of months) won custody of my brother and I. Then proceeded to hate the fact that I was quite weedy and wanted to go back to my mum, plus I look quite similar in the face to her and it probably reminded him of her so I got singled out for extra beatings and just bore the brunt of his insane rage.
One favourite of his was every Sunday having a complete lockdown of the house and my brother, step-mother and I deep cleaning it from morning until night, having to take "mental pictures" of where every ornament was (there was cupboards full of these things, ornamental dogs, china, all that kind of shit) and polishing them all and putting them back in the EXACT same position, and if any of them were out of place we would get a severe beating. Also scrubbing inbetween the floorboards in the grooves with a toothbrush to get all of the dirt out, again, if they weren't gleaming it was another severe beating.
I think prison fucked him up for all that cleanliness shit, and he was fucked up before that anyway. So yeah, he was just a massive douchebag with smallman syndrome. I felt sorry for leaving my infant half-sister and slightly older brother there when I ran away at age 15, but if I didn't I would either have roped or done a "Kip Kinkel" (in minecraft). Plus they didn't get treated anywhere near as shit as I did so it wasn't so horrific for them.