I also do Kroger/Fred Meyer and you are not being fully "informative" there.
If one is signed-up for their shopper bonus plan and you scan/enter your number/member card at the checkout stand you get points equal to the dollar purchase, excluding tobacco, alcohol, taxes, and a few other exclusions. Each $100.00 in purchases will get you 100 points that translate into 10 cents/gallon discount, one time only.
Each 100 points you've gotten can be used to get 10 cents off a gallon of gas, once only, at Kroger gas stations, IF you select that option at the pump. Points are only good for current and next month. If not used they expire, go away. Usually there is a limit of $1.00 per gas fill up.
Your "average 40 - 60 cents off / gallon" means you first spent $400 - $600 in qualifying purchases in the store (inside), you chose the option at the pump to use those points on THAT fuel purchase, you've used during the time period they are valid, and you only get to use them once only and within a two month window at best.
I'll admit it is helpful and fortunately there are many store chains that are part of the Kroger family. Means we can often use those discount points on fuel when traveling across state and to other states.
Here in my state those points basically offset the recent and additional state government tax increase on a gallon of gas of $0.50 !!! Our gasoline/fuel (diesel is included) is at $4.00 +++ per gallon since then. Hasn't dropped below $3.00 for years now, and it's been a couple of decades since getting close to $2.00/gallon or lower.
The single, MAJOR, source of gasoline price increases has been GOVERNMENT taxes increasing, State and Federal.
Meanwhile the roads those taxes are said to be providing and paying for remain in poor condition, increasing crowded/jammed and too few in high traffic areas. Insult to injury, more and more "HOV" (High Occupancy Vehicle = two + persons inside) lanes are requiring a prepaid toll, with sticker attached to scan as you drive by the sensors, or if you don't have that "good to go" sticker, have your license plate number photographed, and bill sent to you in the mail.
Since increased use of electric (and non-gasoline) vehicles has allegedly reduced state revenues from gas/fuel use/purchase (so they claim), now there is talk in state guv'mint of charging a per mile use fee on all vehicles.
Just one of many ways citizens are increasing abused by the Guv'mint that is supposed to be serving us, not the other way around.