There are certainly reasons I can comprehend. I guess it's just hard to see how those reasons lead to 100-200 million people who already had an iPhone getting a new one. I'm sure if I added all the reasons up it would seem obvious but it really does feel mind boggling at first that they're still able to sell so many after all these years.
On the earnings call, Tim’s answer to a question noted that the iPhone active install base is over 1 billion (of the over 2 billion total active devices).
At a replacement rate of 200 million per year, that’s 5 years to turn over the iPhone active install base. Replacing a 5 year old phone sounds pretty reasonable.
