Probably started when they began sticking warning labels like "do not drink out of this hose" on the packaging for hoses due to them being lined with lead.

This is not a feature of boomers here in the UK so my assumption is that this never became a thing here for one reason or another. Maybe lead was never used in UK hoses or there was never a lead-in-hoses scare from the way they approached resolving it or something? I don't know. It seems to be a feature of Americans in particular.