I always carry cash, probably around $100. Not enough that it would be a problem if I got mugged but plenty if I hit a point where I need something essential (food/fuel) to get home or something. I also keep a $20 in the car for fuel if I somehow forget my wallet and run low.
Granted, I only ever use it in a pinch, might as well get the rewards on my credit card instead. But I do on occasion hit a restaurant/store where their internet is down and it’s cash-only.