Thin of the wedge indeed.
I'm no wearer of a tinfoil hat by any means but it is my genuine held belief that the governments of this world would love to get rid of cash entirely, that way all transactions can be monitored.
I have it on good authority that the Department of Work and Pensions forces loyalty card companies to hand over customer data. They use it to establish what recipients of various welfare payments spend on their weekly shopping in Tesco for example and whether it is beyond their means which may suggest undeclared income.
Whilst card use is convenient, even more so with the introduction of contactless payment, we must all resist to temptation to forego cash at every opportunity. The Germans have a good balance in this respect. My recent trip to Berlin exposed me to a large number of establishments that would only take cash, a lot of those were small restaurants, bars etc but it's something to bear in mind when visiting. Even one of the most popular bars in the city, The Monkey Bar, had just one card machine and this was only used by the bar manager, all the other staff could accept cash but he was the sole custodian of the precious card machine. It was actually quite frustrating and extremely inefficient but looking at the bigger picture and with hindsight away from the torturous queues I like the reticence for adoption of all payments by plastic.