I am phone only for payments mostly, but I always have a wallet on me just in case I need my ID for whatever reason. I have also had instances where a shops card reader for some reason hasn't liked my phones contactless, and I have even started to carry a small amount of cash around as you will inevitably get the shop that is having an issue with their card machine and as a result are cash only. I do however only park my car in a car park where I can use an app as I very rarely have change on me. If the car park takes card and their card machine is broken, well unfortunately I am getting free parking there as that is a them problem

successfully argued this on multiple occasions too, even a couple that resulted in them giving me a fine where I successfully argued that I came prepared with a means to pay that they normally accept and due to technical issues on the day YOU were unable to take my only payment method, tickets overturned.