It is weird because it's incredibly ill bred to do that to a person. If you want a picture, you ask, you don't just whip out your phone, stick it in their face and take a photo of them.
I'm part of a group of artist-types that meet weekly, and we're always bringing in new friends. One new person, a photographer, brought his camera and decided to document the evening with photos. I asked him to please not take my picture, he consented... And then tried to do it anyway.
I asked him again and told him it was making me very uncomfortable, and the person who brought him backed me up, but he kept doing it anyway. The room we were in was small so I'd positioned myself where he could get max pictures without having to dodge me, and yet he kept trying to frame things so I was in it. I kept putting things in front of me, or moving, or something, to deter him. I tried to be subtle and not make it a game, as to not encourage him. (I also gave him a few dark looks.)
I was far from the youngest or most attractive person in the room, so it's not as though he was hot for me. I can only conclude that he did what many people do: they take "please don't do that" as a challenge.
I made a polite excuse and left early.
The next time he announced he was coming, I did not attend. (Few people attend every week.)
I was not disappointed when he never returned to the group.
I loathe this mindset that's crept into our culture where if someone thinks that if THEY wouldn't mind having their picture taken, no one else should mind having THEIR picture, either (and to heck with them if they do).