It's because celebrities (other than Princess Caroline of Monaco, mind ... or "of Hanvoer", as she is now) have lost their right to privacy. In becoming (or being born) a celebrity of whichever kind (royalty, nobility, heir/-ess, singer, actor, dancer, sportsperson), their personal status changes in so far as they are more "public people" than you and I are!
When my daughter was only very little, 3 years old or so, she wanted to become a princess in life (many girls do, don't they?). But at that time, there was a total craze going on about Princess Diana ... which ended like it did, we all know how. Despite her being so little, Sabine soon after decided she did NO LONGER want to become a princess "because it is too terrible to have all the photographers run behind me all the time". Yes. That was her statement.
I prefer to be a nobody and not being bothered.
And I wonder if I personally would really take "that one pic of Britney in the gutter", or if I wouldn't much rather pick her up and help her, NOT making any money out of it?
We once had a documentary on German TV on a paparazzo in Florida (I think it was), and how he was "on the prowl" all the time, day and night. Information on who was sighted where or who was going to soon leave this or that house got to him ... somehow, I don't think I ever understood HOW, for one paparazzo would certainly NOT inform the next about insider information he has just obtained! Anyhow, he would hear something and speed through Miami (or so) to get to the mentioned location first (which this featured one never did), waiting, waiting, waiting, oftentimes for a photo op that never came (because Mr or Mrs Celebrity walked out of a back door or so).
That documentary showed that many of them do NOT make the big money at the snap of their fingers. For many it is a 16-hour job FULL of frustrations, since for days, weeks, months they might not get THE photo, or they take one, and the editor of the paper does not publish it.
Though, sure enough, should they ever land THE photo, they make big money out of just that.
Having said all this, it is no plea IN FAVOUR of paparazzi. I am only just telling you what that documentary showed. I don't want to say they actually ALL are poor hard-working photographers, for the PHOTOGRAPHY aspect of their whole job seems geared towards NILL...
And I find most of what they want to capture distasteful. Nothing against a bit of reading up on the princes and princesses of the world when I have to wait at the hairdressers and look at how much their kids have grown ... given those photos are arranged sessions (which they sometimes do in a sort of press conference session).
But those blurred telephoto lens pics of a (known to many) person either just living a normal life (wearing ordinary everyday clothes like any of us would do when we go about our daily chores), and the text saying "Now he/she clearly is on the decline, don't you all see?", or said known-to-many person in distress is just ...
...distasteful to the max!