I always carry cash. I'm surprised when people don't. Came in handy when the hurricane hit, gas stations only took cash. Cash is also good for negotiation.
I say this as someone who lives in part of the US where shops and medical practices are starting to go card only. Having cash is still really handy, though many people here can get by without touching cash for months.
Anytime I've had a body shop repair dents or paint nicks it has cost so much more than $100 that I would literally laugh in the face of anyone that tried that with me.
Not long ago I walked in to a store with $150 of cash and asked for a thing I needed that would be within the amount I had with me and they gave me the $165 item for $150 because thats all I had with me.