One should not assume that those who are not keen on being photographed in public are unconcerned by the high level if institutional snooping, or that they have always felt this way. What has changed is the environment.
Until relatively recently, there was comparatively little institutional snooping going on, and most of that was not disseminated: for the most part, it stayed where it was taken for a couple of weeks, then the tapes were overwritten. These days, it is likely to last forever, and make its way into the hands of those companies that have made it their business to find out everything about us.
Similarly, when someone takes a snapshot on the street, it is very likely to be sucked up into the cloud. Even though I have no account with Facebook, I have little doubt that it can recognize me in the background of other people's pictures, and has a file on my whereabouts and activities.
Therefore, the issue is not the taking of the pictures per se, but the use they are put to by third parties. While I do not spend much time worrying about what could happen as a consequence, I sure do not like it, and I don't think I should have to justify that dislike.