There are a lot of health reasons to scoop your dog's poop. A lot of really nasty diseases are passed through the intestinal tract and shed into the feces. Poop holds a wealth of information. It's like a big warning beacon for illness, broadcasting the fact that your dog isn't feeling so hot for all to smell.
What Can Be Diagnosed From Dog Feces:
Sometimes you tell what your dog has been eating by looking at what they leave behind. Whole kernels of corn, crayon chunks, carrots, other objects that should never have been eaten in the first. (So that's where the Mardi Gras beads went!)
Don't Just Study It
Pick it up and dispose of it properly! Not everyone watches where they are walking, and nobody likes to step in dog poop, or smell it, or see it clearly in their path. It's just not a very pleasant addition to the scenery. And if you don't pick it up regularly, it can be smelled from all the way down the street.