Nannies? Maybe if you're Rockefeller. I'm exaggerating obviously, but nannies are expensive. Baby sitters are expensive too, and is often not worth the hassle.
I have a 2 and a 5 year old, and a restaurant/brewery is just about the last place I want to be with them, and I avoid it at all costs. However, we will occasionally get invited to something where the only option is to tow the kids along, and it usually sucks. You'll probably be annoyed at my kids running around, but I guarantee it's 1000x worse for me...it is what it is.
One of the underrated impacts of parenthood is the isolation. You are now responsible for these living things, and keeping up with old friends is nearly impossible, especially if they don't have kids. If you're lucky, you have good neighbors, which makes it easier to maintain friends.
You wake up and it's insanity until the kids are on the bus, or dropped off at day care. Both my wife and I are off to our full time jobs. Then, in the evening, it pick up time, and by the time I fix them some food, it's probably 6-630pm. Maybe we have time for a walk with the dog if the weather is good, then it's bedtime. and by the time that's done, we may have 1 hour to ourselves to catch up, or watch a show. 90 minute Game of Thrones episodes means we're not getting to bed until midnight! As the kids get older, the weekends get filled with activities.
Sometimes those parents at the brewery are enjoying one of the few times they get to socialize.