With the advent of digital photography, and its ubiquity in recent years, we have seen an almost complete democratization of photography. Virtually everyone with enough wealth to feed themselves has access to a camera, even if it's only in a phone. The DSLR is everywhere. There are now many millions of people with equipment capable of the finest work, equipment which will, when set on Automatic, consistently produce technically fine images.
Pretty pictures, the sharp photographs of a flower or a girl or a classic car, with vibrant and appealing colors, are now accessible to all. I can knock them out all day, so can you, and so can your Aunt Martha who cannot reliably hold the camera the right way around.
The isn't a bad thing, nor is it a good thing. It's just a fact. It has changed the way photography works, however. We now have micro stock web sites, selling outstanding images for pennies. Make no mistake, the work on these sites is often outstanding. These images were made, often, with expensive gear. Models were hired, hours of time spent digitally retouching. The economics are not clear to me, but it seems obvious that in many cases the photographer is operating at a substantial loss. Again, this is not a bad thing, it's just a thing. The market is flooded with people who will work for nothing, because they enjoy the process. You can't make any money playing frisbee either, and nobody complains about that.
What it does mean is that photographs have lost value. Pretty pictures are free. In fact, most pictures are free. Any publicly accessible view of something interesting has been shot, go look on flickr. If you are standing in a place with a reasonable amount of foot traffic, and spot a really neat photograph, don't even bother taking it. Go home, search flickr, you will find 20 copies of the really neat image you saw.
So what still has value? Unique images retain value by their rarity. Photographs of a unique event have value: wedding photography is still a business, because the wedding is a unique event. Sports photography, likewise, as each match is a unique event. News and editorial photographs have value, documenting as they do by definition, unique events. Wet-plate processes, and similar, which produce a unique object produce an object with value thereby. You can also add value to "free" images by packaging them: a book of pretty pictures of flowers has some value because of the labor and curatorial effort you put in to it, the cost of production and materials. A print has some value, although this is decreasing.
This is not to suggest, really, that you shouldn't take whatever pictures you fancy. You should simply be aware that those images will typically have value only to you.