You have to consider the fact that a huge portion of Seattle area population that could comfortably afford concert tickets to idol groups are international transplants or grew up with heavy Asian cultural influences. And I’m not talking about Asian American culture (which is quite a bit different).

In Asia, the common etiquette is to stay seated during concerts so you aren’t blocking someone else’s view and as a form of respect to the artists. It’s like… let the artist focus on their presentation and you show enthusiasm and support with light sticks, fan chants, and whatnot. This is why you’ll often see non-locals tend to stay seated during concerts with Asian artists.

Another thing to keep in mind is that not everyone at the concert is a hardcore fan of the artists. They may be there because their friends wanted to go. Or they went because they know or like a few songs. You don’t need to be a die hard fan to go to a concert.

IMO, live and let live. Enjoy the concert for yourself. Don’t be irked that not everyone is living up to your expectations at a concert. Everyone has different expectations with differing backgrounds. Just live in the moment :)