Gosh what a lot of healthcare professionals!
I think the question was 'why'
Regular alcohol within safe limits is just about the only vice that prolongs life! It can reduce strokes and heart attacks, several solid cancers and may reduce the incidence of other pathology. It was thought this only applied to red wine, but white wine and beer are now known to be almost as beneficial.
Above the safe level the risk is of cirrhosis of the liver, where the normal liver is replaced with non functioning scarring. The liver is the washing machine of the body. We only need 20% of our liver so if you drink too much very little happens until the damage is so far advanced that little liver is left and then you get liver failure. If you are very lucky you may get a transplant but over 50% of those on the waiting list die a lingering death with internal bleeding, coma etc etc.
The other risks are those to the heart (cardiomyopathy or pump failure and also irregular heart beats or arrythmias) and encephalopathy where the brain atrophies and swells causing a wide variety of symptoms from memory loss to senility to psychosis. You may bleed, you may get fractures, your immune system will fail leading to infections and you may get some rare cancers.
Hopefully you wont want this. The problem is what is safe? The published figures were effectively made up and the reality is the safe level varies from person to person. The real risk is that your consumption slowly increases and addiction sets in.
It sounds to me that you should enjoy your alcohol, avoid binging (very dangerous and can lead to sudden death) and ensure you can stop if you want to. If you cant function normally, you may not be developing cirrhosis but you are wasting your life, and this isnt a trial run.