The point is that users should be in control of their data, which means they need an easy way of accessing it. Providing an API or the ability to download 5,000 photos one at a time doesn't exactly make it easy for your average user to move data in or out of a product.

It's typically a lot easier for software engineers to pull data out of a service that they use than it is for regular users. If APIs are available, we engineers can cobble together a program to pull our data out. Without APIs, we can even whip up a screen scraper to get a copy of the data. Unfortunately, for most users this is not an option, and they're often left wondering if they can get their data out at all.