Apple products aren't that popular outside of Western countries ( and the US in particular).
Take India for an example - the iOS market share is a paltry 3.2% for 2019. Ukraine, 13%. Nigeria, 6%. I highly doubt those users are nicely spread to give you full coverage everywhere and not cluttered in the bigger cities and their more affluent parts.
Heck, even France is with 23%, that could easily leave significant gaps in coverage.
Furthermore India is 3.3 million square kilometers, airtags have a range of about 10m.
Which is not 100%. OP literally took 3.2% of 1.3 billions and asserted that was the number of iphones in india (compatible with airtag too).