That's a complex question and I suspect you'll get a wide variety of answers.
In my case I was tired of losing things that I wanted. My self-respect was gone and my wife let me know that my family was next if I didn't clean up my act. That got me started.
Once I got my first taste of freedom from alcohol,though, it was a different story. Freedom, as in that obsession (that hits you at the end of a work day) to drink was gone. I'm never going back. I never knew I was a slave until I was free.