It doesn't matter if you have nothing to hide. Other people do. Many of those people represent you in various official capacities, and you don't want them being coerced. Maybe some of your friends and family members have something to hide.
Also, I find it very difficult to relate to the whole, "I have nothing to hide, so fuck all the other people who do," attitude that many people seem to have.
What you're missing is that people who don't have anything to hide don't want to be forced to adopt hiding practices, even though that might benefit other people. The choice to give away privacy in return for convenience is as much a feature of liberty as the choice to do the opposite, notwithstanding the disutility for a minority that can arise as a result of network effects.
Also, I find it very difficult to relate to the whole, "I have nothing to hide, so fuck all the other people who do," attitude that many people seem to have.