"I have nothing to hide" is heavily dependent upon where you live, when you live, maybe future political administrations. People 5 years ago probably thought abortion was no biggy because of Roe V Wade. Now this might be illegal depending where you live. If you're gay, you would be executed in other countries. Some of us have the privilege of living where it's safe (for now) to live our lives, not so much in other areas.

Everybody should have privacy by default. People should use Signal, don't rely on Google and other big tech services either. Google and Meta was found to be supplying location data information of people who were going to abortion clinics to the police (sauce).

Tangentially, see Mike Montiero's talk, How Designers Destroyed The World. His prime example is Facebook changing everyone's visibility settings by default... leading at least one closeted lesbian teenager to receive death threats from her own goddamn father.

Malice is not required for these decisions to become catastrophes.

Data privacy is crucial.

A privacy data breach that exposes someone’s sexual orientation can have far-reaching effects, including the loss of employment, loss of familial relationships and friendships and even the potential for physical harm or death.

Of course data privacy is important, but I feel like in these cases the problem lies even more with the employer, family or "friends".