Yes I agree. I have some sympathy for single parents who might have to take their kids with them more than they would ideally like but no one should be turning up at a specifically "no kids" event with kids.
I've seen it happen and it always annoys me.
Year 6 leavers' event (evening party) for my sons school. Parents welcome but very clearly stated "NO siblings". One family turned up with their toddler thinking she didn't count though they let her help herself to the food. She was a total pain in the arse. Worst of all both mum and dad were there so one of them could easily have stayed at home with her. The heads teacher's dogs were there (this had been ok-d by the families). Toddler had an ice cream in a cone, kept waving it in dog's face. Dog obliging took a bite of cone. Parents went nuts and believe it or not complained to the governors.
Cousin's wedding. Strictly no kids. Paid a small fortune for a nanny to sit for ours near the venue. Turned up and there were at least 6 other kids present, apparently sprung on bride in last few days when the parents "couldn't" get a sitter.
Friends farewell party (moving away). Asked expressly, please no kids so we can all let our hair down, plenty of notice. Everyone abided except one couple who turned up with 2 kids. WTF? They didn't stay long. I think the hostess, who was quite outspoken, must have had a word or two!
Screaming babies not taken out of theatres, school plays, church services ... I could go on. Some people think their children are so cute and special that the rules don't apply.