[kylehotchkiss]

1) This is never explained to visitors in way that'd get their attention - for example, getting a paper from immigration explaining that's available. Too complicated for now. Maybe once this is available outside the airport it's more viable. Strongly recommend visitors to just take out cash, and carry the amount they need per day + 50% on them. Personally I got by living in India for several years primarily using my American Express card which was accepted at more places than I expected.

2) I wouldn't advise visiting foreigners to get a sim as it requires passing your passport scans to untrustworthy low-level staff at the cell companies. It worries me how they take the passport to a backroom to scan it. I worry they're selling/distributing copies. I realize hotel staff also scan passports but they have reputations to protect and are less likely to. Google Fi/T-mobile roaming or an e-sim via Airolo are much more appropriate and wise choices for short term travelers. If you know somebody in India however, asking for a SIM is totally fine. You can pay to add funds via an international service like Xoom or an American Express card in the Airtel app (which worked for me occasionally)

Protip about American Express cards in India, and the reason I mention it several times. I lost mine last time I was visiting and they sent a new one to my hotel in under 48 hours.