People's lives are busy.They are often too rushed

Why people refuse to give public aid and it becomes more and more usual than before?
People's lives are busy,every one has different reason for every day's life. They do not want to spend too much time on other people,especially strangers. So,they usually ignore other people when they walk on the street,even though someone fell down on the ground or someone really needs them help.In addition,most people do not like to get involved in  the trouble.So,for the above reason,people consider that the best solution is going away when something happen in front of them.
In conclusion,I do not like the situation as the video that teacher plays during the class.Why many people can so indifferent in now society? How long will it take to make a call for a ambulance? How about thinking in this way, what if the same condition happens on ourselves,we also need other people's help.