Simply because it's easier said than done. I have seen the zoo itself and pretty familiar with the lay out as well have seen enough of them to understand the kind of visitors we get at such places- all kinds of people but normal people. Tourists aren't a homogenous group of trained personnel to fall in line without asking a question and obey. Even pulling up a guy ( minimum weight 50 kg) at best while standing over a thin ledge and balancing it is not something everyone can do. It's not a 5 liter bucket of water pulling from a well with the help of pulley. Not when the guy inside the cage is already panicking and the tiger is staring at it. Besides there is no guarantee tiger wouldn't attack even sooner if a rope is dropped in.
So your arguments are pretty naive in this regard. It's really a matter of luck when you are facing a tiger that close.
The situation was different though. In Zoo incident people did try some attempt- it wasn't sufficient and backfired. And I commented because the comments of people making so many arguments about what could be done had become annoying at that time too. The Zoo authorities need to act more strictly to avoid such incidents. If it's you and tiger with no bar between the you two you either better have some weapon or you are on you own. People have died even on Safari hunting.
But you did help didn't you, and still you will be counted among those NCR people who have no sympathy for anyone.
Nirbhaya case- that case had many other serious issues going with it so I am leaving that.
I have lived in NCR for a couple of years and still have to go there time to time. Have a bunch of relatives all over it. From Gurgaon to Noida and in between. The main difference is a large number of daily commuters and diverse population. People who are passing by are always rushing thinking someone else would take action even if they notice.
Still I cannot completely condemn it because I have gotten unexpected help at least twice from complete strangers in NCR and have met some really nice people there. And I have met real jerks in my small town as well.