Everyone as well? Lower costs, better looking carbon footprint, longer lifecycles, better secondhand market, more efficient software (if you don’t assume everyone uses a new phone, you design your apps/web apps with a little more care towards performance and battery efficiency), more competition between manufacturers (because it’s not a given that you’ll sell new devices every 2–3 years)…
Probably. I don’t think it’s much more than the cost of shrinking everything down and shaving 1/2 mm off your design or engineering a whole protocol, chips, and software to pair components together and implement “features” at the OS level to disable some things if it detects new parts.