Authentication is a major hurdle. Back in the days of desktop software, there was no authentication. Mobile apps can often avoid authentication too. Despite decades of web coding, and lots of "this authentication system will make life easy" claims, it is still hard and easy to mess up.
it's impossible to avoid authentication once you start sharing data between systems though. This includes basic stuff like "I only want to share the list with our graduates", as well things like "those preferences should be the same on every device which user X owns".
