Why can’t I set my password over APRS?
APRS messages, even if they are sent from an Internet-based station are sent in the clear and are easily accessible by basically anyone. A password set in this way would not be secure.
To see for yourself, visit APRS.fi and search for your callsign. You will be able to see a list of each of your APRS stations and if you click through, all of the beacons and messages you’ve recently transmitted.