Average income in India (in USD): $422/mo.

Average income in US: $4585/mo.

Considering most streaming/online services are out of reach for Indians, due to cost, and not for Americans, there is significantly lower impact on cell service. 4GB/$15 is isn't unreasonable for most people and can provide plenty of data for Spotify/Waze/browsing. Of course, that varies a lot when you start streaming movies over your dataplan. You'll hit 4GB in no time.

I get 2GB/day and unlimited calls for the INR equivalent of $4.

India is yes cheaper, but not apples to apples. US is bigger. You are also paying to be able to use service in over a large land mass.