The academics are still arguing over whether English is a world language or not but it is the defacto world language and I don't know of another language that can make that claim.
Curiously it's the most widely spoken language while been only the third most spoken native language.
A result of two centuries of the British Empire followed by a century of US dominance in media/business.
The only language that gets close is Mandarin but the split of native to non-native is pretty much inverted between English and Mandarin.
Do you think that users of Firefox in India would like to have “English-India” as one of the language preference choices for the browser? At present, Firefox seems to offer only United States, United Kingdom, and Canada.
In contrast, Mac OS offers eight versions of English for the system language: Australia, Canada, Ireland, India, New Zealand, Singapore, United Kingdom, and United States.
I'm more particular about the input, especially if it's auto-correcting. I prefer "analyse" to "analyze" and other similar changes so I set the software keyboard accordingly. En_GB and En_IN would both be fine, except for the currency symbols. I prefer En_IN because it gives me access to the Rupee symbol (₹).