Fills you up and is cheap/easy to make a lot of (comparatively), making it a staple of many people's traditional diets, meaning we grow up with it being used heavily in our meals and makes it one of the most "familiar"/"comforting" foods, I think. I have relatives who can't eat a single meal without a bit of bread - they don't feel full without it, because when they were younger it was the main thing filling them up. We go to a restaurant, order stodgy food, and my cousin sneaks in a slice of bread for her husband anyway lol