Why haven't you? Maybe because people don't do it. Maybe people learned. Much like you don't hear about people dying of bacteria in the water here in the states at least, much. Why because, people have learn not to drink stuff that hasn't been treated, like the city water. City water being the starter feed.
When Not to Add Calcium
"Young birds should never eat high calcium diets. Having more calcium than they can adequately absorb causes damage to their kidneys and therefore can shorten their lifespan."
So the calcium in the starter feed = regular diet, plus any extra = high