This incident is simply the result of the availability of easy money (early in life, without responsibility and hard work) and a bad upbringing. These girls haven't been taught basic values and propriety. Their only concerns are daaru, disco and ladke, which isn't all that bad except for the fact that such brain-dead, moronic, retards (of which Delhi at least has a huge surplus) have never exercised their brains in any other regard.
No wonder they were grounded by Air Sahara for indiscipline and misbehaviour. What they needed was a good round of slapping in the police station last night at periodic intervals. It also seems that professionals in India, like the security agencies and news reporters, have a long way to go before they can act maturely and not be taken in by the puppy-faced, dreamy-eyed charm of attractive, English-speaking girls in attractive clothes.
Their car could've had a terrorist with a rocket propelled grenade launcher in the trunk without them even knowing anything. And then today our headlines would've been markedly different.