For most people a phone is a monthly payment. One of the rewards that keeps them paying is that every few years they get an "upgrade." The phone companies and the mobile carriers very smartly followed the car model of selling: they sell a payment, and when the balance is paid off they offer a trade-in/upgrade (and a new loan). If you resist, you eventually stop getting support.

For the same reason, many car dealerships don't work on cars more than 10 years old. They keep their techs focused on the newer stuff, and increasingly pressure owners of older cars to trade them in.

Fortunately for car owners, there is a robust market of, and legal requirements to allow, parts and independent service shops for older cars. We don't have nearly that kind of support for older phones.