re: Do you add milk to scrambled eggs?

Dairy fat coats egg proteins and slightly inhibits their coagulation when cooked. This provides more leeway to cook scrambled eggs all the way through, before they become tight, overly firm, and dry.

You can achieve the same effect without milk or cream - but in that case, your timing needs to be perfect.

Also, the flavor becomes richer (and more interesting, IMO) when the eggs have a touch of cream.