I do to for similar reasons. But I will use debit if the merchant extends me a discount, one of the gas station here for example gives me 2 cents off per liter

I do to for similar reasons. But I will use debit if the merchant extends me a discount, one of the gas station here for example gives me 2 cents off per liter which works out as more than the rewards. However, I never do cash cause I never have cash on me. It's Credit for reward and then debit. That said, I know a lot of people who don't do the rewards maximizing. Programmer/engineer crowd tends to self-select for people who are logical and number inclined.