In financial UK devices, displays primarily enhance transaction security and user experience by enabling OTP generation, transaction verification (e.g., amount/payee details), and digital certificate management to prevent MITM attacks and tampering. They provide operational guidance (e.g., PIN prompts) and support MFA (e.g., fingerprint+OTP). Future trends include smart interactions (touchscreens, biometrics, QR code banking) while balancing security and cost.