When I was drinking my primary relationship was with the bottle itself, not really the people in my life, I just went through the motions of trying to please them and was very self-involved. I would have denied this at the time... as the denial of my condition perhaps extended to other areas of my life and relationships. I went through similar too with an addicted family member.
With both sides of experience, I would never try to be a 'rock' to an alcoholic or an addict as I think it's unhealthy in an emotionally involved relationship, and really just an addict's excuse in many cases to avoid getting their own help. It can tear you apart emotionally however, as I still loved the addict... but not their illness.
I know what you're getting at but as an aside, your title stood out to me, as I believe we're all here for a purpose and reason, to learn through living. If I didn't believe that, I'd probably give up the struggle pretty quick, as nothing would make sense.