Asklemmy

You could make a super long argument against this but I think there's a few simple points (that you can use any number of, you don't really need all of these at once for most people) that usually get it across to people, at least from my experience.

There's the moral/emotional argument:

"You do have something to hide. Wanna unlock your phone and let me go through all your messages/photos/emails, leave the bathroom door open all the time, and never close your blinds? Even if you aren't doing something illegal AND have no problem with me seeing all your conversations and data, privacy is still a comfort for many people"

...and there's the monetary arguments:

"If a company is collecting that data, it's because they make money off it. It's a multi-billion dollar industry, and it's the only reason Google, Facebook, etc can physically exist. If they know more about you, they can manipulate you into spending money with advertisers easier, allow political campaigns to manipulate your opinion more effectively, etc"

"You might not have a problem with how your data is used now, but if the law changes, or a corporation decides to do something different, suddenly data about your health and finances that was just for ads might then become a way to increase your health insurance pricing to the max you can afford"