Sounds to me like the startups you have had the misfortune to work in have a maturity problem. Yes, startups drink. But most of the world drinks as well.
That doesn’t mean that you should be surrounded by a bunch of immature asshats that can’t readily accept people who don’t choose to do everything they do such as eating meat, drinking, etc…
I work in a startup with a lovely team of people who would never pressure anyone into drinking or anything they felt uncomfortable with because we are mature and thoughtful people who actually care about the people that we work with and accept that we aren’t all the same.
You have been unfortunate to choose workplaces who have a culture that you don’t fit with. It isn’t fun and you shouldn’t have to deal with that in a professional environment, but you also have the choice to leave and find somewhere that you feel comfortable and you are appreciated for your ethos. Find mature, like-minded people that are doing something meaningful and don’t be afraid to stand up for yourself!