Sainsbury’s self-service checkout is aware but not helpful

I was buying a few things from a Sainsburys local at lunch time. I used the self service checkout stand and scanned my items in. I then “used the touch screen to complete my purchase” as the voice said out loud to me. I inserted my card but didn’t press the “debit/credit card” button. I got an error: “please press the card button”. Clearly the machine is aware that I’ve inserted my card because it’s giving me an error message. The question is, what does it need to give me an error? When it detects that I’ve inserted my card, it should jump to the card payment option automatically and allow me to enter my PIN. There are unneeded steps in this process.