My friends and I take week long trips in Baja on our dirt bikes. We ride hard and fast over difficult terrain, and hurting ourselves isn't out of the question. An expert rider in another group doing what we do crashed and died on the first day. After the situation was dealt with, they continued on with the trip as planned, as each of them felt that if they were the one who died, they surely wouldn't want that to ruin the trip for everyone else. I feel that way as well.
I think JW's feel the same way. In the event that I witnessed, I think making people get up and leave would have been more disrespectful than staying. They are a big family after all, and I think leaving would have been akin to seeing your brother have an attack and then getting up and leaving. Even if asked to do so I doubt any of us would. I think I felt like it was supporting the family by being there with them, even by sitting there observing.
I would say that the JW's in the audience felt like the riders felt in Baja. They feel this is an important event and if they were the ones having the attack would probably insist if they could that the show go on for the benefit of their friends.