I'm sure it's not rare as in unheard of, but to have any significant impact on the number of people carrying 2.3 billion devices, there would need to be hundred

I'm sure it's not rare as in unheard of, but to have any significant impact on the number of people carrying 2.3 billion devices, there would need to be hundreds of millions of people with multiple phones. I have no idea of the statistics, but I wouldn't think it would be anywhere near that common.