At today's Huddersfield fair, I had a conversation with the guy next to me on this very topic. He made the very valid point that every time you pay for a £50 purchase with cash, the recipient has £50 to spend on something else. If he uses that cash in the same manner, the next recipient will also have £50 spend. But if you use electronic payments the bank takes 2 or 3%. So a £50 transaction at 3% leaves the recipient with only £48.50 to spend. When he spends that sum electronically on a subsequent purchase, the recipient only has £47.04 to spend. That reduces to £45.63 for the next one etc. Within 8 transactions, the banking system has extracted 20% of the original value. If the transaction is funded to £50 every time, it would take over 20% by the fourth transaction. If cash was used, the full £50 would be available ad infinitum to all except the banking system. The banks might not like cash, but there is no need to involve them if cash is used in person to person transactions, or at least within the local area. Purchasing power for the masses is actually enhanced by not using cards (debit or credit), because there is no mechanism to skim off the fees. Yes there is a case for having banks for remote transactions, but not for putting every transaction through their system when cash would be more cost effective. Whilst there is always a security risk in carrying large amounts of cash, the benefits of using it are not insignificant.
The modern view of things only costing a fiver for some fee that is avoidable with a bit of thought and planning is part of the wealth problem. Book a hotel through a booking site and you pay £5 more than you would if you call up the hotel and book it yourself. It's not rocket science. Rhetorical question, but why do people buy things off ebay from me with at least a 15% surcharge to the cost of the item on the website when they have been pointed in the direction of the latter previously? Sure it involves electronic transfer that has a cost to the vendor, but they are also saying please fleece me as the buyer for 15% more. People really do not think.
The solution is in all our hands.