Imagine if you have an antivirus on your computer. If you don't give that antivirus access to your disk, it won't be able to analyze your files for viruses and protect you from other software. The concept is similar with PrivySeal. It analyzes part of your Google Drive to let you know what sensitive data the other apps can know about you. If it doesn't have access to Google Drive, it will just be another advice-providing application.