Yard cleanliness and yard odor reduction.
If only poop smelled like flowers. Since it does not, poop removal is a must in order to get rid of the undesirable smell.
Your yard will be more enjoyable.
Removing the poop will get rid of the odor and the likeliness of your dog or you stepping in a stinky pile which will allow you the opportunity to make the most of your yard for outdoor activities.
Poop that is not picked up can become host to diseases and/or parasites. These diseases and/or parasites can be transferred to your pet(s) and/or people that come in contact with it.
Prevents stool eating.
Some dogs eat their poop or the poop of other dogs and/or cats. Stool eating is known as coprophagy. Stool eating can cause intestinal issues and also lead to your dog ingesting parasites if the poop they are eating comes from a dog with parasites. If you scoop the poop, there will be no poop for them to eat.
Pet waste is not fertilizer.
Cow manure is the most commonly known form of animal sourced fertilizer. The difference between cows and dogs is their diet. Cows eat plants while a dog's diet consist of mainly meat which causes it to be very acidic and bad for the lawn. Poop left on lawns can cause what is known as nitrogen burn on grass.
It is the law.
There are many reasons why you should scoop your poop. Here is a great hand out from the EPA