Hello nelsons21
The Cable Operators (MSOs) have complete control of what cable modem/gateway hardware they will allow installed and the firmware it uses, this is because they own the coaxial cable that is connected to the ARRIS SBG6782, because of that the Firmware updates are pushed by them, and any update needed as well. Any associated firmware updates are automatically deployed by the cable operator. This is not an ARRIS only implementation, but the required implementation of any cable device manufacturer.
Even for the device owned by the customer only your internet service provider can only update firmware since they are the one activating modem and to check the current firmware version you can see on the modem interface.
Let us know if this helps.