I know, it's a shame because it is so obvious when you look at the signs, but because there were never an episode that really delved into it, people just don't seem to get it/forget
I think that it's incredibly difficult for anyone growing up in that kind of situation, where they only relationship role model in their life is two people that fight & drink all the time to go on & try to forge their own healthy relationships in their adult life. Of course Xander had trouble with it all.