"Using a screen today means squinting and pecking through prompt after prompt, comparing alphanumeric strings and other details between the screen on the hardware wallet and the screen on whatever device you're using with it. When this process results in a final decision to approve a transaction, the hardware wallet uses its private key to sign the transaction so that it will be accepted by the bitcoin network onto the public ledger.

Are you sure this is the right amount? Did you copy paste the right address? Where did you get this address in the first place? How do you know malware on your phone didn't modify the transaction details or ask the hardware wallet to do anything that you didn't intend?

Screens on hardware wallets can help with some aspects of these questions -- but we think in practice they are often used in a way that doesn't achieve the protections customers hope to get from them."