Because it is not a static scenario. Internet users in India grew by ~30% over last one year itself and that growth is not slowing down. And FreeBasics is not limited to people coming on the internet for the first time.
free basics is doing that at a rate of 50% per month. (according to them)
i doubt people would want to shift to free basics from a full internet and if they do then that's what they like, its their choice. We should continue using normal broadband. Now you can argue that telcos will then overcharge for normal broadband, but who knows, they might not and even if they do then TRAI can send them a notice to not do that, and they will stop like they did with the "fast lane" thingy.
That stat is misleading when you compare percentages against raw figures:
1 million: Free Basics users in India in 2015 (source: FB press release)
5.8 million: Data users acquired by Reliance, FB's sole partner in India, in 2015 (source: IAMAI)
109 million: Data users acquired by all telcos in India in 2015 (Sep 2014-Sep 2015, source: same IAMAI report)
So if Free Basics converted 50% of their users to the full Internet, that's about 500k users, or less than 0.5% of the industry's success rate.
Asking for dangerous policy exceptions because your flawed scheme has an actual success rate of 0.5% and presenting this as 50% is disingenuous at best.
There are some people who are using "free basics" now that wouldn't have any Internet access without it. Now, you could argue and I'd probably agree with you that it's bad in the long term, creates a distorted market etc.
But if a foreign company offers a net subsidy to access a part of the Internet shouldn't that drive down the price of Internet access for everyone? I.e. you could access "free basics" and also have a complimentary Internet subscription that could be offered at a lower price since your Facebook traffic would be subsidized.