Utilize your financial knowledge, give your answer or opinion to the input question or subject . Answer format is not limited.

Why are earning credit card rewards often tied to groceries and gas?
Every reward program has to have a funding source. If the card gives you x percent back on all purchases. That means that their business is structured to entice you to pump more transactions through the system. Either their other costs are lower, or the increased business allows them to make more money off of late fees, and interest. If the card has you earn extra points for buying a type of item or from a type of store (home stores improvement in the Spring), they are trying to make sure you use their card for what can be a significant amount of business during a small window of time. Sometimes they cap it by saying 5% cash back at home improvement stores during the spring but only on the first $1500 of purchases. That limits it to $75 maximum. Adding more business for them, makes more money for them. Groceries and gas are a good year round purchase categories. Yes there is some variation depending on the season, and the weather, but overall there is not an annual cliff once the season ends. Gas and groceries account for thousands of dollars a year these are not insignificant categories, for many families are recession proof. If they perceive a value from this type of offer they will change their buying behavior.  My local grocery store has a deal with a specific gas station. This means that they made a monetary deal. Because you earn points at the grocery store and spend points at the gas station, the grocery store is paying some compensation to the gas station every time you use points. The gas station must be seeing an increase in business so theoretically they don't get 100% compensation from the grocery store.  In cases where credit cards give airline miles, the credit card company buys the miles from the airline at a discount because they know that a significant number of miles will never be used.