A lot of zigbee infrastructure also expect an internet connection.
These border routers also double as admins, and people want their smart home stuff to be available while they are outside their home network.
Thread devices can mandate internet connectivity the same way Wifi devices can.
Matter defines profiles and does certification that says your light bulbs cannot require an internet connection. The admin your water leak detector connects into can (and arguably should) alert you even when you are away from home, but the leak detector _itself_ cannot do that and be certified.
These border routers also double as admins, and people want their smart home stuff to be available while they are outside their home network.
Thread devices can mandate internet connectivity the same way Wifi devices can.
Matter defines profiles and does certification that says your light bulbs cannot require an internet connection. The admin your water leak detector connects into can (and arguably should) alert you even when you are away from home, but the leak detector _itself_ cannot do that and be certified.