To me it is almost entirely the sound. I am really not into nuances etc. And if we are just talking about UK...well, does that not include Wales? Certainly some of them would expect to sing along, at least this bunch

http://www.youtube.com/watch?v=SMI5wpwXTCY&feature=related

It also includes many immigrants. We know of the great singing cultures in Africa..New Zealand..Estonia..Hawaii..

Anyone can have any preference they want but they shouldn't assume everyone knows what the local practices are, and be in a huff about it. Just explain what it is. And don't assume they come to specifically hear the performer. Sometimes they are dragged along by a spouse etc. Sometimes it is a social night out. Sometimes they might have just sort of stumbled in, so say up front what you want. If they don't like that rule they can leave. But don't look down your nose at them either for trying to show off by knowing all the words. That is sheer nonsense for someone who likes to sing. Some of us quite happily will sing along and leave great gaps in the words anyway.

People tend to assume that others see things and hear things as they do. This is just not so. Nothing wrong with liking things a certain way, and acting to make it happen how you like it. Seek like-minded people. Put locks on the doors or have secret passwords if you need to keep certain types out...I have no complaints with that...but the level of disdain for those who do not see things like you do is too high for my taste. mg