I did question this with a friend of mine who used to set up these networks . I did vent my frustration at him once and I was given the following explanation.
Indian Pre Paid ( pay as you go) SIM cards can only bought after giving ID proof etc.This is not the case with SIM cards in other countries ( I.e I can go and buy a pay as you go SIM from my local shop in the UK without any ID proof).
This was the reason why the wifi access (though free) was limited via the requirement of an Indian mobile number.
It is a different matter at the lounges though. Most lounges have the same WiFi access password for everyone which defeats the whole purpose of requiring a mobile number.
