The author didn't say that you can't have alcohol in events. The example that they gave was that at the networking event all the drinks were alcoholic and the server had to struggle to find a non alcoholic drink for them.

Following your example, their experience would be akin of having a lunch event at a work event were they only had pork for eating when chances are that in the group there are probably some vegans/vegetarians or people that due to religious belief abstain from eating it. The argument is not that you shouldn't have pork. Is that you should also have some more options.

Yep and when you go to a catered event, you often don’t have any real option to eat if you don’t eat animal products. At least at an event where they serve beer you can just drink water.

In either case, you’ll get weird questions and you might feel left out.

My group has a very strong drinking culture and I don’t drink and don’t eat animal products. I’m always in situations where I have to explain why I’m not eating or drinking to our customers, but my coworkers and our customers are adults and don’t make it weird.

I'd actually empathize better if that had been the argument - I'm not even strictly vegetarian but it's not unusual for work-related social functions to operate on the assumption "everyone eats meat" (with maybe an occasional exception). The last such event I went to I didn't drink (not a major issue, I was fine with sparkling water), but nor did I wish to eat meat (which I do maybe once a week at dinner - this was a lunch). That proved basically impossible as it was share plates and all but one (which I insisted on, despite objections) had meat.

That might be true in the US, but there are plenty of cultures where it's common not to eat meat, or exclude certain kinds of meat. I remember the time white American co-worker told one of our Indian co-workers, a devout Hindu, that his food had beef in it. "Just a joke", right? Lots of east Asian countries have essentially no dairy products in their mainstream diets.