It is the difference between you being able to have control -- by exercising judgment and discretion in order to prevent an invasion of your privacy -- and being able to seek only "post-injury" relief in the courts by complaining about the invasion that has already occurred. It is the difference between preventing the injury, and trying to get damages after you've suffered it.
If we're talking about a broken arm, isn't it better off to prevent the broken arm in the first place?
With privacy issues, we are just not talking about accidents. Many "invasions of privacy" can be prevented. It just takes some effort and mature judgment. Just because we live in a society where many of us -- and especially the young -- do not hesitate to share "too much information" with everyone else does not change the fundamental equation.