Why doesn't my husband care if our son likes him or not?

We became empty nesters 8 months ago. Our son turned 18 and moved out a week later even though he's still in High school. Our other kids are older and both of them have children now. My son was always a momma's boy. But when he was little even if he preferred me he still loved daddy. He turned from momma's boy to I hate daddy boy. He started really disliking my husband when he was about 11 and my husband didn't care. He said he's not here for our kids to like him. And I agree. But my he never tried to get to the reason why our son hated him. Our son would rather walk home than ride in the car with his dad. I told him to go with his dad to the store to help him and he told me no. I don't think it's because his dad was strict because I was stricter than his dad and he still adored spending time with me. My husband now says he has daughters and grandsons who love him so he doesn't care if our son hates him. But over the years he put in little to no effect to find out why. My son lives with a friend and I'm allowed to visit him but he says his dad can't. I ask him all the time why he doesn't like his dad and he just says it complicated and won't talk about it. I've been trying to push my husband for years to try to build a closer relationship so we can have a close relationship with all our children but he doesn't care. Says our son is an attention seeker. Is it normal for a teenager to just hate their dad?