Yes, but there is a significant difference between what I may observe walking down the street in that very momentary glimpse and what is permanently captured in an image that can be seen not by a handful of people, but by thousands of people, or in fact by millions or tens of millions of people when the image is put on the Internet.
In fact, that's one of the challenges posed by these types of technologies. We all observe things in passing and we probably forget about them, but when that image is collected, retained, and can be seen in perpetuity by tens of millions of people, suddenly the privacy balance shifts dramatically.