Probably something to do with the level of exposure. It seems most Indians know English pretty well, but not as many have taken that last step from "know" to "fluent". It's difficult and probably not strictly necessary.

Also, en_IN and en_SG are just different from en_US and en_UK. Apparently in southeast asia, "do the needful" is a perfectly cromulent phrase. (My main complaint is the seeming lack of consistency when using "the". Sometimes they use it, but most of the time, they don't. This makes emails very hard to read. Just when you were enjoying the literary experience, a "the" is missing and it jars you back to reality. But I digress.)