I fail to see why the fact that a pub serves food should immediately turn it into a glorified ball pool. Do adults not eat too?
But that's just the point - it should not turn into a glorified ball pool, just because there children there. As someone has already pointed out, these are "adult" spaces and kids should behave accordingly. If a pub has put play equipment in the garden, then fair enough. But otherwise, I expect them to sit and eat/drink quietly. Like roz, we usually only take the boys into a pub when out and about, as somewhere for a reasonably priced, fuss free meal - hence the no food, no kids suggestion. Like ghis says, they can get bored and fidgety - which happened to us in Hastings recently when it took over an hour to produce our order of fish & chips and ploughmans, but we managed to restrain the little darlings from trashing the place.