That's exactly the same issue with ticket, Oyster cards, ITSO cards and contactlless (Bank Card) transactions. Passengers decide to get whatever form their ticket is in when they get to the gate rather than approaching the gate. Personally, unless both hands are already in use, getting a card wallett out of my pocket and presenting the ticket to a reader. A phone is something different, it will need the login screen to be woken up, a PIN entered, the ticket application opened, and the ticket loaded onto the screen before presentation. Those who think that phone based virtual tickets are faster need to consider how long many others take to pass through and not assume that everybody should be as fast as they are.