Not just customer expectations. Consumer law and the internet...
When I started out in the late '70's you basically sold it and if you even gave a receipt you'd write 'sold as seen, tried and tested' or some such nonsense. If the customer came back (not many did) you might have a bit of an arguement, maybe wave the two-foot breaker bar at them. You'd hear no more. Nowadays customers have the CRA and will write bad reviews from here to kingdom come. They'll also turn up waving printouts from internet forums etc ....