This is technically already a rule in most places in the US. It's not a "3 drink limit" but just that you are not allowed to serve alcohol to someone who is int

This is technically already a rule in most places in the US. It's not a "3 drink limit" but just that you are not allowed to serve alcohol to someone who is intoxicated and most people would be legally intoxicated after three drinks in a short(ish) amount of time. It's just very rarely enforced. I suspect the reason is mostly that probably 99% of bars would go out of business if they could only sell 3 drinks per customer per night. Alcohol, like many things that are fine(ish) in moderation but really bad in excess, as an industry is completely dependent on problem drinkers. They are a small minority of alcohol consumers but make up a hugely disproportionate share of total spending on alcohol.