I've actually heard that it's also used by smaller businesses as a way to communicate with their target audience. So, for example, if you are a chain of cinemas, you can let everyone keep up with when/where you are going to release the next films. If you are a retailer, you can advertise when the new products are in.

A bit like they did in the past with email newsletters. (Though a lot better: for a start, it doesn't spam your inbox, which can remain for more important matters).