It’s because of everyone’s need to fit in. Teenagers are in that weird limbo state where they have a need to fit in but don’t have the maturity to say, “No, I don’t need an iPhone just because Billy has one.” And they generally have access to the money required to fit in, either because their parents will buy it for them or because they worked enough to get one.

For the record, I don’t blame teenagers for this. The decision-making part of the brain (the prefrontal cortex) doesn’t even finish maturing until their mid-20s. The part of the brain that deals with emotions (the amygdala) matures way before then, so they’re impulsive, emotional, and not rational (or at least not even close to how rational the average adult should be).