You speak as if a phone is gold bullion, which has no other value than to store value. Also note that time is also valuable, and can't be easily bought.
There may be a really good reason for a not well-off family to get a new and advanced phone from the phone company, for a small monthly payment. They can't afford the upfront cost, and will pay more for a depreciating asset. On the other hand, they now may have a phone with a great camera to record their kid's school graduation, or other such event that only occurs once. Or they may finally use a smartphone with 4G / 5G to have good-quality video calls with some faraway friends or kin, which were a pain with their old phone. Etc.
This still beats buying a new phone with a credit card, at 29.95% APR.
There may be a really good reason for a not well-off family to get a new and advanced phone from the phone company, for a small monthly payment. They can't afford the upfront cost, and will pay more for a depreciating asset. On the other hand, they now may have a phone with a great camera to record their kid's school graduation, or other such event that only occurs once. Or they may finally use a smartphone with 4G / 5G to have good-quality video calls with some faraway friends or kin, which were a pain with their old phone. Etc.
This still beats buying a new phone with a credit card, at 29.95% APR.