Joy's first husband, Bill, is described as unreliable. Why?

From the text:

As the love haze wore off, Joy began to see that the same qualities that had made Bill so attractive as a college romance— his free and rebellious spirit, his nearly paralyzing contempt for “the Man” — made him a completely unreliable husband. And she discovered that what she had foolishly thought of as his typical low-level recreational drug use was really something much worse. In a time of drug experimentation and excess.

As the years passed, Joy kept hoping that Bill’s alcohol and drug use would fade. She was caught in a familiar trap for young women and girls — the fantasy that she alone could change her man. So she doubled down on the relationship. They had a child together. She hoped that would motivate Bill to make some changes. But his addiction just got worse, and the physical, mental, and emotional abuse he unleashed became more intense.