Cameras are expensive. Photographs are almost worthless. Supply utterly outstrips demand, especially for shots like landscapes that have great appeal for amateur photographers but little commercial utility.
Ten years ago, you could name every paparazzo working in London. They were a small circle of time-served photogs who knew everyone, and whom everyone knew. There was an infrastructure of couriers and darkrooms to get images from film to press in time. They spent years cultivating relationships with celebrities, doormen and nightclub owners. Today, there are countless PJ students and teenagers hurtling around Soho on scooters. With a cheap DSLR and a smartphone, an image can be on the front page of dailymail.com in 20 minutes.
The new breed see their work as a more exciting alternative to working weekends in a shop. Most of them are happy to get a quarter of what images used to sell for. They shoot using the modern equivalent of "f/8 and be there" and need practically no technical skill. Rather than cultivating relationships and building sources, many of them rely on Twitter. Unlike the previous generation, many of them are happy to tip each other off and share information. It's now scarcely possible to make a proper living and most of the old-timers are shooting commercial work or weddings.