We always went too. Sometimes due to conflicting activities or when I was sick, only one of us would go, but I can't think of any event they ever did that at least one of us wasn't there.
I have seen this before though. I know I talked about the friend of my DS who was on the football team who had come from Africa. His parents never attended one event. Not just his football games, but when he got inducted into National Honor Society, or on scholarship night, the year end banquets....ANYTHING!! I would always take his picture with DS at the NHS induction, scholarship night, etc or events like that and then make sure he had a copy. I know on senior wk in football the parents decorated their son's lockers. I knew he wouldn't have anyone do it, so I took extra stuff for his and decorated it too and then took pictures so he'd have some. They weren't even there on senior night when they introduced the players with their parents. Luckily he had an older brother that came for him though to that. Funny thing was at the games, all the parents would cheer so loudly for him. I think everyone knew about it and wanted him to feel supported. He didn't go to our middle school, but the other football parents from that school said they'd never seen them either. So very weird. It didn't seem like it bothered him, or else maybe he just didn't act like it because he didn't want people to know it bothered him.
Same thing with orchestra. Most of the best players in DD's orchestra were Asian. It was a common occurrence for them to not attend events even if their child had a prominent role in the concert. These rest of us who never missed an event were always puzzled by it, but again, the kids didn't act like they minded. I know we even would drive the 1 1/2 hours each way to DD's college to watch her play in a concert for an hour. She said some of the kids commented they couldn't believe her parents were always there.
I think maybe it's just a cultural difference or at least in my kids cases I think it was as they were more immigrant type situations.