Why do restaurants give you bread?

What do just about all restaurants have in common? Tables, chairs, cooks in the kitchen, servers, and menus all make a whole lot of sense... without those, the place wouldn’t really be able to call itself a restaurant. But what about bread? Even though some restaurants have started charging for it, just about every sit-down restaurant will bring you bread at some point between sitting down and get your food. But have you ever stopped to think why? Isn’t the point of a restaurant to get you to spend money on food, not fill you up for free before your meal even arrives?

This question was recently posed on Quora, and commenters posited lots of different theories. We lay them out as simply as possible, here.