Want an answer from an alcoholic? (I'm from the school of thought that addiction is addiction--same disease, different drug of choice.) If not, feel free to skip my reply.
I think most of us don't realize the pain we're causing others during our addiction, because our minds are so extremely focused in ourselves and in our own pains and anger--fancied or real. Addiction takes over our minds like a "beast".
Many of us are "blind" to how we are being because we are so hyper-focused on running away from our feelings that frighten the he** out of us.
I sometimes wonder if our psyche also causes us to deny that we're causing pain to others in order to protect itself. I know for me, I was so full of shame, regret, guilt, remorse, and self-hate, that I couldn't really face what my actions were causing others because that amount of self-hate piled on would just be too much to handle. So sometimes our addictive minds justified how we were acting.
I will say that I have both experienced and witnessed people who get to the other side of honest and thorough step work to be able to see the pain they caused, to feel badly about it, and to make sincere amends for it.
We're not all self-absorbed people although it certainly appears that way when in addiction or if we're not actively using in addiction but have no emotional sobriety. Our authentic selves I firmly believe are not this self-absorbed. When I'm spiritually fit, helping others and thinking of others becomes natural. We grow up and allow ourselves to feel the growing pains, finally getting that feelings won't kill us... we stop running from feelings and fear.
I think the only exception may be if someone has been diagnosed with something like Narcissistic personality disorder (not just "narcissism") but I could be wrong. That's just an opinion.
I hope that helps.