It's a fair question. I'm not the person to whom you replied but thought I'd contribute my view point.
I don't carry cash because it feels more cumbersome and less speedy than paying with card. With cash, I either have to work out close to exact change or--when I'm out for a leisure day and going to several places--have a mass of coins jangling around at the end. I've noticed that I'm now irrationally irritated watching someone painstakingly count out $12.83 in exact change ahead of me at the till.
It also makes it difficult for me to track where I'm spending. That $60 or $100 might have gone to eating out or a bookstore or some other random place. I'd rather have the card transaction to know and categorize for sure.
Speaking of denominations, I'd rather not carry much money around on me yet ATMs around me only dispense in multiples of $20 and then you get into the fun dance of how to get smaller bills if needed. So many shops now say "no change made."
Finally, I put all of the spending I can (basically everything except mortgage and student loan payments) on cards for the card benefits. Miles, automatic cash back, in-store discounts, etc. Those don't happen when paying by cash. (Yes, I know, the benefits are being paid out of the transaction fees that the merchant is charged plus interest that other people pay. I'm aware that I'm leveraging that and that prices would, possibly, be lower overall if we didn't use cards or didn't have the rewards. If that day comes, I will adapt.)