Yes, but you forget that a lot of parents, when they take out DC to pubs, whether this is on weekends for lunch or in the evenings, some of them don't allow their DC to behave well and/or expect other people to tolerate them, because, you know, they have children.
One time recently I was in a pub for a Sunday lunch date, family of 8 in total next to us, included a 4/5 year old, 2-3 year old and a baby and a 8-9 year old and 2 sets of parents. We were sat blocked in fairly close together with not much of a gap between tables, we couldn't move table though requested to, pub was rammed anyway. Baby starts crying, mother attempts to soothe/feed it, after 5 mins still full on crying, she didn't take it outside (nice weather too, no rain), baby continues to cry and scream for the next 10 mins. 2-3 year old starts fighting and trying to play with the older child who's playing on an ipad which has the sound fully turned up, no ear defenders on. Parents weren't engaging with these children apart from to say, "stop that, be quiet" and then returning to their meals, drinks. Then the 2-3 year old throws a bread roll (not at us luckily!) which lands near another older couple's table. The father of the child says 'Oops, say sorry Tarquin (made up name!)' Tarquin, "silence". The meal carried on like that for the remainder of their time there though admittedly there was laughter and fun noises from the table, albeit quite loud. They were both upper class families in a pub in an upper class village in SE London. When they finally left, a bit earlier than I expected to be honest, we breathed a sigh of relief, but our time was up anyway from our meal.
I actually know one of the bar staff in there (it's a sort of regular of mine) and mentioned this briefly to him when he saw me and asked how my meal had gone. He sighed and said 'we can't do anything about it, but it frustrates us and Sunday lunches are our bread and butter, we realise the impact on other customers though, sorry your meal was spoilt by their behaviour'. He also mentioned that the mess some of them leave behind is appalling, vomit sometimes, not cleared up, dirty nappies left there, food smeared on tables, chairs which includes soft furnishings of chairs.
This is in a pub in a naice area, on a weekend, god knows what it's like elsewhere!