The primary reason is a of the mobile app. Unlike the web interface, the app does not always provide a one-click option to compress a folder into a .zip file for local storage. Other potential blockers include:
The inability to download a folder directly from the Google Drive Android app is often due to a lack of a native "Download Folder" button in certain versions of the mobile application. While the desktop version allows zipping folders for download, the mobile app often restricts users to downloading individual files or making them available offline. Why You Can't Download Folders Directly can't download folder from google drive android