I'll repost what was posted in reddit if some people haven't clicked the link:
In China, this kind of situation is referred to as the 'Peng Yu' effect. Before you condemn then, you have to understand their situation. The law right now in China means that many victims of traffic accidents, or people who have fallen ill in the street have actually successfully sued the people that helped them for sums of money that could easily destroy lives, even if there is no evidence that they are the ones that caused the accident (because they were not). There is a China Daily article on this topic.
In a country that executes more than any other, I wonder how willing you would be to potentially implicate yourself in a crime by helping a stranger. Yes, its very sad. But I, for one, find it hard to blame them in this situation. The law needs to change before people can become less suspicious.