During install, why does the Android app need access to modifying or deleting SD card contents?

For the app to work offline so that you don't need a constant internet, the session data is downloaded to your device. This also enables high performance to browse, filter, and search through massive conference programs of thousands of sessions and presentations.

Whenever the organizer sends a new data update, the file is stored in your device's memory. Old data files are cleaned up by the app automatically so the app keeps the smallest data storage footprint possible on your device.