None of us normal folks know what's going on in any alcoholic's head. We can only guess: The reason he or any other addict walks away from a partner is because being single gives one more time to drink. "I said to him at one point he was always drinking or tipsy when I arrived to his house on weekends and he hadnt been like that before and I didnt like it. " You have now caught on the the pattern and are agitating for change, which would be a normal reaction. It's not an effective reaction, but it is a normal one.
He didn't change. He just stopped trying to pretend to be normal. Alcoholism is progressive. There are many alcoholics who grow accustomed to drinking large amounts every day, and gradually, the urge to drink overwhelms the desire to go to work [ or pay attention to a spouse, nurture children, engage in hobbies].
My husband drank a lot, even though his parents were tee-totalers. Eventually, his company was being disbanded and he knew he'd be out of a job. He chose to stay to the end and go on unemployment. It wasn't until the unemployment benefits were about to run out that he even made a pretense at looking for work. By that time he'd spent a year at home, and he was in the habit of drinking even more. He did get a job, but now he was hungover many mornings and arrived late, and his cravings caused him to leave work early to get home to start drinking. Some days, he barely worked six of what should have been eight hour days. He lost this job and then two more, each time spending his time unemployed drinking more. Each time he found work again, it was a a lower-level job, with less benefits, and a pay cut. At the end, he was just full of excuses at to why he couldn't look for work - - but the real reason was, now he couldn't go eight or nine hours without booze. And truthfully, at that point, he probably would have needed to be hospitalized to detox safely.
Over the years he drank, he stopped engaging in hobbies. We didn't go anywhere or do any thing unless there was a steady flow of alcohol available at that activity. That's the nature of the beast.
The US has really, a horrible drinking culture. In many communities, getting wasted on one's 21st birthday is considered a rite of passage. Teenagers drink too, and consider it a huge joke. The number of parties I've been to where people talk about getting stoned on cannabis and how hysterical it is to go out driving that way is appalling. I wouldn't say it's country-wide, but in some families drug abuse is a multi-generational experience. Sometimes children are removed from their parents' care owing to the parents' drug use, and the grandparents are addicts as well, so the kids end up in the foster system or raised by great-grandparents (probably not an optimal situation, either.)
We no longer see Foster Brooks acting out scenes where he's a drunk dentist or drunk airline pilot (he was kind of a one-trick pony) but frankly, I don't think the attitude has changed. It just not politically correct to portray it humorously on TV. Some countries may have a culture where spending time in bars is a way of socializing. I think here maybe more people drink at home, but most addicts minimize or lie about how much they drink. Different symptom, same result.