I have read similar articles a few years back. The "missed call culture" as people put it has been there for quite sometime, since the mobile revolution in India. However I would say one reason for this might be that voice mail is hardly used in India - if someone's phone is unreachable or switched off - when you try calling them, you hear a recorded message saying the other person is unreachable - unlike in the US when a lot of times you are just redirected to the receiver's voice mail box. I happen to be not very fond of voice mail :(