This most likely means that people love the iPhone so much that they’re willing to carry it along with another phone that they need for some other reason, and possibly even pay for two phone plans at once. Most likely explanations:
- They’re required to carry the other phone for work.
- They had another carrier for the other phone, but they’re not yet out of contract.
- They recently switched and got a new phone number, and they’re carrying the old phone so they can get calls on the old number until people switch to using the new one. (And nobody told them about call forwarding.)
This shows that they have a lot of very devoted fans.