But basically when someone wants you to drink it's their social anxiety that is manifesting, not yours. They need other people to participate in the bonding ritual, part of which requires people letting their guard down, which alcohol helps with.
But I'm not sure it's the chemical pathway that does it. I mean yes, drink enough and you will feel different. But you open up socially over a beer before the beer has any effect, eg. while you're waiting in line at the bar chatting to someone, or while you have just a tiny dose in your blood. Likewise with drugs, I never thought I was getting especially high or changed somehow. So perhaps it's more like a Schelling point, people accept that alcohol/drugs at a social event means that you can relax.
I've also never felt that I became someone else when drinking. Even when so drunk I couldn't walk straight, I could still understand social cues and conventions, and I still knew what I desired. It's like the beer is an excuse for bad behavior rather than the cause.
Luckily as an adult with kids I don't get badgered into getting hammered anymore. But I did think of a good excuse after talking to a cardiologist: you can always say you have some sort of condition that makes it a bad idea for you to drink or do drugs.