This happened to me last year in the Pacific Northwest region of the US.
A woman had approached me at a gas station, first asking for some money. I told her no, and she started making comments about how her sick grandma was up in a hospital somewhere, could be the last time she sees her, etc; typical sobstory scam lines. I again told her no, and she asked if I could put some gas in her car instead. Again I refused, she called me heartless, walked over to the next pump, and gave that woman the same schpiel (that woman gave her a 20 dollar bill).
Later, that same day, I stopped at a different gas station (+ convenience store) near the first one, because I was thirsty and it was on the way to where I was going. On my way out of the convenience store, I noticed the same woman from earlier giving another woman the same schpiel. I was curious about what would happen, and she didn't seem to notice me, so I hung around in my car for a few minutes to see what happened.
The scammer ended up giving her a nearly verbatim schpiel, except this time it was how her baby-daddy wouldn't let her see her daughter. This woman ended up filling up the tank (~12 gallons if I recall), she said how thankful she was, got in her car, and drove away. Sitting in my car behind this other woman, I noticed that she had a "Baby on board" sticker in her window, which tipped me off that the scammer was likely changing the story based on the audience.
The next time that I was in the area, about a week later, I needed to get some gas again. I pulled in, pumped my gas, and was waiting for the receipt to print when she comes up to me again (probably not recognizing me), giving me the same schpiel, but this time it was her father needing dialysis. I called her out, told her that she'd already asked me when it was her grandma in the hospital, and that I'd seen her ask when it was her baby-daddy not letting her see her daughter.
She told me to mind my own business and to "strongly consider" going to different gas stations in the future before driving away.
The possible benefits that I could think of for this scam were
- If you (the scammer) ask and the mark gives you cash (perhaps because they're afraid of skimmers), you get free money
- If you ask and they give you some gas, you can then drain the gas into canisters to resell for 100% profit. On the chance someone buys you a full tank, you have to get rid of the gas somehow before you can execute the scam again
- If you run into trouble, or the gas station attendant tells you to buzz off, well, there's always more shifts, and more stations to try your luck at