Fair point. As you said, you can test the mobile app without signing up. We found that many of our users didn't know about our account syncing feature (because they didn't sign up). They then told us that it was difficult to switch between devices when they downloaded our apps as they had different news sources on different devices. This is an effort to remedy that confusion by keeping one single consistent account across platforms. Trying to get users to sign up later when they want to sync (which we've tried on mobile) has proved to be difficult for most users.