[ghaff]

It's modern electronics vs. mechanical or even simpler analog electronics (modulo leaking capacitors and the like). You can absolutely buy a watch today that will last for decades plus--but you and a lot of other people presumably prefer a smartwatch instead. Perhaps the day will come when electronics can be designed in a way that replacing hardware isn't necessary to improve/update them but it's hard to see the path to that in the near future for non-trivial devices.