Jimmy,
What you are describing is the chlorination of water done by the city water supply company or what you have to do if you have your own well to get water. Chlorination will kill the fecal bacteria that is present in the water taken by the water treatment plants from the lakes and rivers. Both of us agree on this part, but I am talking about another problem that exists in India.
Once the treated water (chlorinated) water enters the pipes to go from the water supply company in India to the houses of the city dwellers, it can get contaminated because of breaks in the system. The amount of chlorine present in the water that reaches your house is not enough to kill the bacteria that enters the pipes between the water treatment facility and your house. In addition, the chlorine cannot kill the parasites that are present in the fecal matter and can enter the water supply system in between the water treatment plant and your house.
Because there is lack of 24 hour continuous supply of water from the water treatment plant to the houses and because there are breaks in the system, most people in India put filters in their taps or boil the water. Countries like USA, Canada, UK, Singapore, Japan, Australia, etc where there is continuous water supply do not have to do so.
Addendum:
here is a link to what I am saying:
Intermittent water supply Read page 31(Consequences)
".....No water from an intermittent water supply system is safe to drink, because under vacuum conditions foul water can be drawn into the pipes. ...." You will find more detailed explanation if you read any Public Health textbook.