The process of obtaining a P2P ticket is not at all intuitive. I struggeled the first time I had to get one. As I can see it, there are a number of reasons why a passenger may need to get a P2P, not just the "No card. No problem" splash-screen scenario that Northern are pushing.
1. Maybe I do have a credit card but I don't actually want to use it to buy my train ticket. Perhaps I want to pay by cash or Rail Travel Vouchers.
2. Maybe I want to buy a ticket that the machine cannot sell e.g. rovers, sailrail tickets, Northern newspaper special offer tickets, Priv discounted tickets or a ticket either a different origin than the station that I'm at, etc. I may want to pay by cash but equally I may want to use my credit card.
3. Maybe I want to buy a ticket using my credit card but it is above the cost limit for TVM sales. I'm not sure what the limit is but the TVM at Steeton wouldn't let me complete the test purchase of a first class ticket to Thurso!
The current process of having to select a destination and a fare, and then telling the machine that you want to pay by cash doesn't cover many of the possible scenarios. Perhaps the machine should just say something along the lines of "This machine accepts credit/debit cards only. If you want to pay by another method, such as cash, or if the machine does not list the ticket that you want to buy, then please obtain a Promise to Pay ticket by choosing your destination station and pressing the "Promise to Pay" button. You will then need to pay for your ticket on the train or at a station on your journey".