I think it’s entirely a regional/cultural thing.
Here in Australia, it is normal to address a priest ‘Fr Smith’, unless he asks you to call him ‘Fr John’.
And I think this is just an extension of the cultural norm of calling someone ‘Mr Jones’ until/unless he asks you to Call him ‘Bob’.
Then again, I think just ‘Father’ is the more common form of address, depending on the circumstances.
Our diocese has two priests over from India, and we just call them Fr Matthew and Fr Thomas - because their last names are quite hard to pronounce.