I agree with you about a watch. I've had the same watch for the last 30 years - it's electric but has it's own generator to charge the battery so doesn't require me to change batteries every few years and it only cost £30.
Smartphones are different because they're mini computers. I rarely use the phone element but am constantly checking emails, looking at weather forecast, news, location maps and so much more - it's my Hitchhikers Guide! So when did you last change your laptop or desktop? I rest my case...