Is it normal my friends dad doesn't kick her boyfriends ass?

So last week I went to visit an old friend I haven't seen since high school. (Its been almost 10 years.) She lives with her dad and had just broken up with her abusive tweaker boyfriend earlier that day.

They said I could stay the night on the couch and I fell asleep. A couple hours later her dad woke me up saying I had to go because the boyfriend was coming over to pick her up at about 4am.

There are so many things wrong with this picture. First why is she going back with him in the first place. Second why the hell is her dad allowing this? What the hell is wrong with him? If I had a daughter hanging out around some tweaker piece of shit who hits her he wouldn't be around to be coming back in the first place.