There were dozens or more different desktop and mobile RSS apps which used Google Reader as their back-end. As soon as Reader shut down, they all lost their abi

There were dozens or more different desktop and mobile RSS apps which used Google Reader as their back-end. As soon as Reader shut down, they all lost their ability to have Reader download all the content from the cached feeds and sync to the client when connecting, which allowed people to have their computer off for days and come back without losing any content from their feeds (many feeds have 30 or less items at a time, and if you don't check for a while, you'll simply miss many posts). New syncing systems came up in its place, but it fragmented the market and different apps started using different backends, or their own paid backends, and there was no longer a de-facto standard backend protocol that everything supported.