This trick is not unique to Pakistan, I faced this twice! in UK and US. I was with family on a motorway services, pulled in for fuel and a break, was approached by young gori female driver with two kids in the back seat, she asked for help as she has run out of cash for fuel and will return the money by cheque in post later. I wasnt fully sure about her, so i asked i will not pay cash but if she get the fuel i will pay the bill. She wanted my address, for privacy and security i didnt want to share the details so asked her to forget about it and paid fuel bill direct to station. I was satisfied that she was genuine, i got the fuel for my car and decided to have break at services later. after a while i was leaving the service, noticed that lady still trying to get help from several other drivers, so that was a con. As most people get the fuel and leave services so dont realise this and falling for this age old tactic. I wasnt pleased with myself while driving off and promise not to help again, there is a reason begging is crime in UK.
Second incident, a asian uncle approached me in Las Vegas, after a initial chit chat he asked me for help with fuel and he stuck and had to travel to another state. Though being Asian i wanted to help but the whole situation and bad experience in the past, He was not on motorway but Las Vegas strip ( main road), a hub of gambling and casinos, an Indian uncle may have run out of gambling money so I refused after his insistence I just walked off!
Though in this material world, human values should be part of community, if you suspect just walk/drive away. Only help if its safe and sure it will be of any help. Always think would you do that if you are in same situation? Probably not, only professionals do it with confidence!