They get their name from the fact that they were originally designed for bike messengers and courier but they have evolved to be used for a lot more than that. They give you a flat and protected space to allow you to store many different items.
Due to this, there are a lot of different uses that they can have. Not only this but they are also highly stylish, meaning that you are going to be able to look great while you are wearing. This is a highly convenient bag that is going to be useful time and time again.