I always wondered "why" too. Who would want to choose such a chaotic life, but my Dad did. I decided early on that he was nuts and I wanted nothing to do with him but that's because of physical abuse. The one thing I did do to try to fit into his life was the lies. Answer "a" one day and it worked, answer "a" the next day and it didn't work. Rethink and wonder what answer would work, try "b" and it worked. The next day it didn't. He was so messed up, he was just evil. And I mean that.
I read a brief story of one alcoholic answering his "why". In his case he was a married man, 45, with three kids. He said he had really been drinking since he was 12. He was hooked and alcoholic. He said that he really had quit maturing at 12 but was a man of 45. Imagine trying to solve the problems of a 45 year old with the brain and maturity of a 12 year old. Pay the bills, care about an adolescent daughter, deal with a wife, keep up with the house, keep the car running, on and on. This is what comedies are made of, the 12 year old trying to take care of life like Tom Hanks in Big. Even if he wanted to he had no skills to pull it off.
This totally enlightened me, I had never heard of that before. And it made sense. This is exactly what my Dad was, a twelve year old trying to take care of business. Not only that but he was a mean twelve year old. At least it answered my "why".