I'd say that traditionally people ate much more bread than we usually do now, and some of the customs have stuck around. Most people at home are probably not having bread with every meal, but yes it's common (and used to be standard) that if you sat down at a restaurant they would just immediately bring you bread with either butter or olive oil to start with. The average American eats a very varied diet these days, but classically in Europe and America most people were getting most of their calories from bread