I don’t expect they get anything out of it, I think that type of person just has absolutely no understanding of the fact that everyone in the entire world isn’t exactly like them. They lack the ability to understand that their experience is not automatically your/my experience and are completely incapable of accepting that you or I might not think or feel or want exactly what they do.
Perfectly put.
A lot (absolutely by no means all) of extroverts just cannot understand that some people are introverted and see it as a major personal problem and a serious character flaw, for which you require urgent 'help'. The same kind of 'help' we see on MN when people who are very worried about not being able to pay their rent and council tax are advised to book themselves a fabulous weekend in Paris, to chill and take their mind of it. A smile and a "Wanna join us?" is fine, but if you decline, that's the end of the matter.
Also, because it's a common extrovert trait to be egocentric and feed off the energy of others (not necessarily in a bad way), they will often see you acting differently from them and interpret it as you judging them. They think that you're there inwardly frowning, focusing your disgust on them and despising them for making themselves look like an idiot whilst you do the 'proper, dignified' thing; when, in reality, you're probably not actually thinking of them at all - and, if you are, you're likely thinking that you're happy that they're happy but equally very glad to just be able to sit and chat or enjoy the music/event in general in your preferred way.
As PPs have said, some people are like it with non-drinkers too. See also people who go on endlessly about football and demand to know whom you support, when you genuinely hate it (yes, even when it's England playing) and see it as utterly tedious and pointless for you, whilst remaining perfectly accepting of and happy for people who do like it - because you're a grown up and you understand that different people like different things.
People saying that you just shouldn't go are being ridiculous and extremely unfair. I think they're either the type of extrovert described above or have anxiety from being targeted by said extroverts. Dancing is only one small part of many social events, so why should you have to miss out entirely just because you prefer to chat and just listen to music instead of dancing to it? It's like saying that vegetarians should feel compelled to stay away from weddings and big celebrations, simply because a proportion of the buffet won't be what they will want to choose.