No one uses cash at starbucks. It's all phones, credit cards and debit cards. Try and buy a beer on a plane. They don't take cash.
I don't know where you live, but in the UK cash is still common, even with tap and go on cards. Also what planes have you been getting on? They usually take cash in a ton of different currencies.
Every plane I have been on in the US refuses cash and only takes card.
You can still easily pay with cash on planes in Europe, I've taken around 4 flights last year and I was always able to buy some drinks and snacks with cash.
Now on topic, I'm personally still using Bitcoin to buy food through takeaway.com, even with the higher fees it's cheaper than using Paypal or debit card, as they charge a 1 euro fee for that.