Even if you don't care much about your own privacy, sharing too much or too widely can lead to a loss of privacy for everyone.

Much of privacy law is based on a "reasonable" expectation of privacy. What counts as "reasonable" can change depending on what people in general believe it to be.

Here's an essay [1] by an appeals court judge from 2012 for some more on this.

[1] https://www.stanfordlawreview.org/online/privacy-paradox-the...