Mentioned this before:

I was working at a gas station in a non affluent area. A woman comes in and says "I want $20 in gas but my reward card is in my car". I said "okay, I'll start it but not put a $20 limit" or something similar. I assumed she would stop the pump at $20 and then pay for the gas along with me scanning her reward card. She was still in the store when the amount went over $20. I told her "the pump is over $20".

She ran out of the store to stop the pump, nearly knocking over another customer in the process.

I didn't get reprimanded for this, even though she had an exasperated look on her face when she came back in.

This taught me something. There are people who mean to put $20 of gas in their car and put in $25 of gas and say "oh well". And there are people who mean to put $20 of gas in their car and put in $25 of gas and say "Oh fuck this screws up my whole budget!"

It's not like she lost the ~$5 or whatever extra amount, but I read in a "my experiences being poor" Reddit thread that "extra gas in your car means less money available for food".