If your employer decided to praise you verbally, instead of giving you a paycheque, would you be motivated to keep working for that employer?
Food is directly linked with survival, so it is extremely valuable when used as a reinforcer for preferred behaviours. Rewarding dogs for preferred behaviours with food, increases dogs’ willingness and ability to learn, and makes training an enjoyable activity to engage in together. It also makes you pretty awesome! The frequency of food rewards is high at the start of learning, and is reduced over time when the dog has successfully learned the desired behaviour.
Feeding a dog it’s kibble in a food bowl is literally hundreds of wasted daily opportunities to reward it with something it loves, food, for doing something for you!
Think of paying your dog with food for a job well done. He'll want to keep working for you.