During the last couple of years I had acquired 7 cash/rewards cards, monitoring them consumed more of my time. I'm now down to 3 (soon to be 2) cards, I did make some money with bonuses and cash back. But, with the isolation mentality, I don't fly nor go out to eat much. I was always looking for an edge.
I was able to charge my property taxes, auto expenses,,,etc to the cards and was somewhat profitable. Then the powers that be decided they were losing income so most started charging fees. 3% here 5% there, our medical center gives us a 5% discount if we pay cash. I found that paying cash was simpler and saved me more, gas became $.10 a gal cheaper if I made the effort to pay cash est. $3.50 - $.10 works out to a 2.38% discount better than the 2% I had been earning.
The big downside of the cards manifested itself in more and more unnecessary purchases, Amazon in particular had made their goods more costly, negating any rewards (also, that brown van was making many more visits to my house). I had to remove my card info, trying to make it more bothersome to buy on a whim.
Some people swear by them, but I find myself better off if I forego the cash back and simply ask for a cash discount. Cash is real, credit is fleeting and costly.