First, we need to use the hardware wallet to receive and send coins. To receive coins, you need an address, and you have to tell the outside world what the address is for receiving coins; to send coins, you need to prepare an unsigned transaction first, then the hardware wallet will sign the transaction, and finally the signed transaction will be broadcast to the blockchain network, and then the coin sending operation will be completed.
Therefore, the hardware wallet needs data transmission, otherwise you can't receive coins and can't send coins.
But data transfer does not mean that the wallet is connected to the network, it is only done through USB or Bluetooth.
Because the hardware wallet itself is not networked, it usually requires a cell phone, computer, etc. for use.