There are a _LOT_ of services that treat the URL as a secret. If you're leaving these URLs in your browser history on a public computer other people can access them. For example, the images served up by Google Photos, that have the form lh3.googleusercontent.com/[kilobytes of base64-encoded spew], can be accessed by anybody having the URL. So if you use a public computer to access these, even though you need to be authenticated to browse Google Photos, and despite the fact that you conscientiously logged out, anybody with access to the history can still look at your photos. This is not be any means the only such example.