Why do people put milk or cream in their scrambled eggs?
The milk adds more protein, fat and vitamins as well as making the eggs have a creamier texture. Many people use thicker higher fat milks or half and half (you can even use heavy whipping cream). To give it a slightly tangy taste you can also use sour cream.
Another reason they're added towards the end of the cooking is to cool the eggs down so they stop cooking once removed from the heat.