Since Covid I have gone virtually cashless. The only regular recipient of cash is the window cleaner. Other than that any purchases from small market traders and in summer the ice cream van!
When traveling I have used cards wherever possible, but made sure payment is in local currency - never use the 'sterling scam'.
I can't see what additional useful information an airline is going to glean based on my on board purchases, other than I'm a sucker for overpriced grotty sandwiches and snacks!