Orange juice with calcium & vitamin D?

I moved to the US about 2 years ago. I did not have much culture shock, but there was one thing in the supermarket here: orange juice labeled ''extra calcium & vitamin D." I had never seen something like this before and I could have not figure out why until I took this Marketing course.
They want you to replace milk with orange juice in the morning!
Drinking orange juice is a breakfast-thing here in America. But people drink milk, too because they think it is good for their health - for the calcium and vitamin D. Now, some people think poring themselves 2 glasses of beverages in the morning is too much. So the orange juice companies thought, "let's make those milk drinkers start drinking orange juice if they were drinking milk because of the calcium and vitamin D!"
Orange juice companies were perhaps afraid of losing the juice market share to the increasing number of new juice varieties. So they tried to take the share of milk in the home breakfast market, which they saw an overlap with milk. Of course, some people maybe drinking milk for the proteins or other nutrition facts or the taste. But more people probably value the calcium and vitamin D.
This got me thinking about two things. 1) even a market driven marketing strategy can change our habits or lifestyle. 2) if so, how much of our habits and lifestyle is actually shaped by marketing?