5. They make you make better life choices
Being on a good diet makes you make better choices about food.
But a good diet is also likely to make you consider exercising more, sleeping more/better, taking care of stress in your life and relaxing more, and various other things that make for better general health and a lifestyle much more conducive to weight loss.
Basically, the effort of dieting is only worthwhile if your lifestyle is healthy, so a good diet will motivate you in other areas too. Good deal!