Like it or not, society sees classical music as up-tight.
"Leading scientist ejected by audience after 'trying to crowd surf' at classical music concert" 
>Before the performance, Mr Morris invited the audience to bring their drinks into the standing area in front of the stage and instructed them: "Clap or whoop when you like, and no shushing other people."
When I think of fun shows I've been to, I don't exactly remember any with audience reminders that showing enjoyment was permitted.
I don't dispute that (I of course dispute that they're correct in thinking that, but not that they think that).
That classical music is inherently "not fun" is what I responded too -- and my argument is in the past classical music was very much appreciated by all kinds of middle class and working people in Europe.
>When I think of fun shows I've been to, I don't exactly remember any with audience reminders that showing enjoyment was permitted.
Another problem is that enjoying art == having some kind of crash fun, like teenagers at spring break.
Of course, I'm biased, because I'm one of those people who likes attending classical performances. But its for the same reason that I don't want 3 televisions blaring while I'm eating a fancy meal.
At a certain level, distractions take away from the enjoyment of the thing you're concentrating or enjoying.
I don't think there's anything uptight in this: I could say the same thing about people turning on the stadium lights during a mosh-pit/rave.
Its as simple as some human experiential dimensions exclude other human dimensions: we can't, biologically for the most part, experience or investigate the full extent of all our senses at the same time.
Sitting still and enjoying art is orthogonal.
Some might not like sitting still, but that doesn't make sitting still incompatible or constraining the enjoyment of art in abstracto -- just for them.
I read this claim as physical expression of emotion is entirely voluntary and consciously constraining physical response does not change the experience. And for the people who it does, it's a matter of socialization not human nature.
This type of perspective - even if true (I disagree but will not discuss here any further) - is why classical music is up-tight.
The idea that one must jump, dance, and prance around as of paramount importance is more tied with teenagers setting the agenda of "popular music" since the 50s or so, than some inherent human need.
That's because you've learned how to act and what is acceptable in those circumstances.
Would you expect someone from 1850 to just appear at an EDM club and know what exactly is happening?