@r_alb as I live in the US, this argument has been more effective lately: whether something is worth hiding depends on whether it could be used against you. Some things like your credit card number, SSN, or home address are obviously dangerous to give to a malicious individual, but as we're seeing today, even information like your political affiliation could be used quite powerfully against you if known by your employer, ICE/CBP, etc., or companies who could sell it to them such as Amazon.
This doesn't always get people to start caring about their own privacy, but it usually works to get people to understand why a lot of people do care and even need to care about their privacy, which I think is a good first step.
It often helps to shift the narrative from "privacy only helps criminals" (which is a mentality too many people I've encountered have) to at least "lots of people need privacy but I don't think I do" and once they're there it's a lot easier