It is entirely a matter of supply and demand.
If no-one was interested in seeing Brittney falling over or what ever other sad behaviour she is doing right now, there would be no photographers taking pictures of her.
The fact is western society has created a multi-million pound industry based on the need of people to point and laugh at famous rich people brought low by circumstances.
It's mean, and nasty and small-minded, but it sells millions of pounds worth of magazines and papers every day - so that's why these photographers get the pictures, and why they can charge four-figure sums to magazines to print them.
Education in the concept of being nice to our fellow human beings would eradicate this sad sleazy trade - but since we can;t even educate people not to drink themselves to death, I'm not really holding my breath.