Luvk9s suggests scheduled feedings (twice a day, once in the morning and once in the evening) versus free feeding (where food is left out for the dog all day long) for the following reasons:
It is difficult to come up with a regular potty schedule for your dog if he is eating all day long.  Most dogs that have regular schedules (for example, eating at 8 AM and 5 PM) also have regular bowel movements.
 Dogs tend to overeat if food is available 24/7.
 In a multiple dog household, it is difficult to monitor how much food each dog is getting.


Visiting dogs who are used to scheduled feedings could cause issues with food that is out 24/7.
Dogs tend to get finicky about their food because they are really never hungry.
 In a dog’s life, food is the number-one motivator. Sure, they love rides in the car, going for walks, playing fetch or getting a visit from the neighbor’s pet. But nothing beats food. A dog with no passion for food is an unhappy dog. A dog should have an unbridled passion for food. They need to look forward to their next meal with anticipation and excitement. This creates the foundation for a well-tempered, happy pet.
It is difficult to do training (using treats as a motivator) if the dog is not hungry.  

Allow 15 to 20 minutes for your dog to eat his meal and remove any left over food. Let your dog’s gastric juices and digestive system take a rest in between meals.

Luvk9s Dog Training