I like things that sometimes contradict themselves or make no sense at all.  This song is crass, but it's rock and sometimes rock isn't pretty.  The girlfriend is really skilled in the bedroom, but she's otherwise crazy, he kept her around or keeps her around because she's wicked good and brings out his animal nature.  It's rude, it's demeaning, it's crazy in and of itself, but that's what I like about it.  Is it art - who cares - its lusty rock and I'm sure there are real guys out there who similiarily stay with a woman only because she fulfills a need and there are women who do the same thing.