why not help?

it was night time when couple stroll in the well-known park in town.......it was a great night to walk and also enjoy the moonlight.........actually they are waiting for the child to finish work and send her back...........suddenly a bike come from the back............then in flash moment..........something emergency happen........the bike appear to be snatch thief.....where they snatch the handbag of that women.........hopeless at the particular moment.............the women was in shock while the man seem want to catch up the bike.......there are a lot motorist pass by and some ppl walking .........if one of motorist apppear helpful then the thief can be stop.........but no one help........the thief juz escape like that....izzit at the particular moment all the motorist cant see it was an emergency?????o the situation is too dark to make them see the clear picture..........o it was ambiguous situation where the bystander thought there are a movie shooting!! o the bystander said it none of my bussiness..it not my responsible ........i m not the police...........o there are ppl who know how to deal wit the thief...........o the just think this is another snatch case.........i cant do anything.............o the scare the thief have weapon that might hurt them.....o the media influence which tell ppl it nt worth to help-newspaper on last few publish a news about a kind helper that help police to stop the crimimal and get hurt coz being shoot by police...........o it simply that the world is too unsafe to being helpful......who know u might become victim coz of show help...........does that mean help someone will cause risk to urself.......prosocial behavior ..........o simple there are hard to find a real altruism which unselfish care for other welfcare........o there are reasons ppl dint help??????????????