I too have made friends with strangers I've met in bars, as well as with servers and bartenders at places I've been a regular.
Here's a book that can help you stop thinking it has anything to do with luck:
How to Talk to Anyone: 92 Little Tricks for Big Success in Relationships [1]
[1] https://amazon.com/How-Talk-Anyone-Success-Relationships/dp/...
A tip if you do decide to try this advice, don't let anyone know you aren't drinking. Not only will you often get accosted "Come on buddy just one!", but at the end of the night you will often be pressured to become some sort of unpaid Uber.
For sure some people are extremely obnoxious when they drink, especially heavily, myself included (which is a reason I don't like getting drunk - I try to stay mildly buzzed if I do drink, but usually I don't at socal gatherings, unless they are major social gatherings, and I even usually only drink water at bars) but the vast majority of people are fine after a couple brews. Most people stop getting blasted at around 25 or so anyways.
Your attitude indicates to me that if your perception of someone changes when they've had a beer, just because they've had a beer, rather than their actual behavior. I don't mean to be rude when I say that - I can understand. I used to not be able to stand being around people when they were drinking. I avoided anywhere where I thought there may be alcohol... but that was because I grew up with an abusive alcoholic father and I was projecting my hatred of my father onto other people. It wasn't until years later I learned to be comfortable around social drinking. I learned to realize that my father did the things he did because he is a bad person, not because alcohol somehow forced him to.
As I said in another post, I actually ended up meeting the person I ended up marrying in a bar!
(I also did start drinking myself later on.)
To be clear I don't want to put you down or anything, just sharing my perspective.
Very likely. There are bars where people go to be alone; bars were people go in a group to stay purely within their group; bars where people go to meet between regulars and are closed to newcomers; bars where people are opened to anyone, regulars or 5-minute newcomer; etc.
The most classy, and also often the most hyped ones are the coldest ones. The most popular are often the warmest... providing that you manage to get into the 'family' circle if it is a matter of regulars/locals; or that you belong to the same scene if it is a subculture oriented place.
And it also depends also on you. And not necessarily as you expect. I am amongst the most introverted, shy, less talkative persons ever, and yet bartenders and regulars generally great me by calling my name on my 2nd or 3rd visit in a bar while some mates who've been coming to the same place dozens of times in are given the cold shoulder (I have plenty of examples like this, it was quite funny sometimes to see how upset by the situation my mate was :-).