Before answering that question, we want to make it super clear we do not want any of your personal information nor do you have to give it either! If you choose to use Sign in with Apple it gives us a proxy email and logs you in completely anonymously. Also, you can just use a fake email if you do not want to sign in with Apple and do not want to provide your actual email. See below Q for more information on that.
The two main reasons for signing in are customer support and troubleshooting issues for users. If you are having a problem we can help figure out what is wrong by looking at your account. Also if there is an issue we want to be able to let you know. We have never, and do not plan on sending you marketing emails of any kind.
We also have you sign in because it helps us keep the app secure. There are so many new and awesome features in the app, including social features that you can choose to take part in or not. With that, we needed to beef up security as well. The sign-in is to protect your information.
Lastly, we are looking to add a suite of new apps that you will be able to share your data across! This means that you can start a project in one app and then easily transfer it to another.
If you are really not into signing in you can also just turn on airplane mode and open the app. This gives you the stripped-down version of the app that does not connect to our server.