I have been doing this for 40 years, I rarely pass a stranded motorist on the side of the road, while assisting I tell them my help is not free, I charge them with assisting 3 people they encounter. and each person they assist is to be charged with assisting 3 more and so on.
Recently I saw a guy at an auto parts store buy an alternator and go outside, as I left I saw him squatting against a pole making a cell call. I was half in my truck but something screamed "I have a problem" so I went back to him and said "You look like a guy that could use a lift". Turns out the pulley on his van's alternator came loose and stranded him about 20 miles north of Laramie and an off duty sheriff's deputy had given him a ride to the store and said he would try to get another deputy to give him a ride back to his van, but no one was free.
I gave him a ride to his van and told him that once I was injured in a fall while working (installing communications wiring) and the service truck they gave me when I started back had a faulty fuel gauge and ran out of gas at 1/4 tank. My arm was still in a sling (full thickness rotator cuff tear) under my coat and I was seriously limping from a broken pelvis and how no one would help a one armed man limping down the road in a snow storm with a gas can, so I do not pass someone in distress.
When we got to the truck, I had to make a U turn through the interstate median and as I pulled up behind his van he said I had made a change in him and from then on he would not pass by someone in trouble. I said "Good because my help is not free, you owe me helping 3 people and each is to be charged with helping 3 more and so on". He said "YEA! Pay it forward, like in the movie, I'm gonna help more than 3 and pass it on".
I really don't think I could count the number of people I have helped and charged with helping 3 more, I have no way of knowing if they all did, but maybe a few actually paid it forward.