It's not the device whis is made obsolete (objectively). It's a very specific group of users who perceives it as obsolete (subjectively), since they want to always have the newest thing. Other people are different, and will be happy to pick up one of those "obsolete" phones at a discount and use it until they physically fall apart.

For example, I'm just switching phones after having used a 2nd hand phone for 8 years. Screen was broken for years, battery is struggling more and more, freezes are getting too frequent to ignore. Another reason for the switch is, there's more and more apps I cannot install because my phone is too old.

The last point is a good reason for your argument, discontinuation in support. When they stop supporting my old device, that is making it obsolete. But whatever new stuff they release in the meantime does not affect me at all.