Let's use a orange juice as an example: 
 When someone see on a label "natural flavor", it doesn't mean that it uses only orange flavor, or even contain orange extract at all, this flavor it's created also with extracts from bark and grass.

But if companies want to approximate the flavors as more realistic as possible why do not just use "oranges"? The answer comes down to availability, cost and flexibility, where according to flavor chemist Gary Reineccius, of the University of Minnesota. "At one time, there were 10 times more grape-flavored products than grapes grown," Reineccius says. "If you're going to use all your grapes on grape soda, you don't have any for wine. It would be exceedingly expensive. Then what do you do with the byproduct you create after you've sucked all the juice out of the grape?".

Natural and artificial flavors are that different at all. While natural flavors are created by extracting chemicals from natural ingredients, artificial flavors are made by creating the same chemicals synthetically.

The main reason for companies bother to use natural flavors rather than artificial flavors its only by one reason: MARKETING!

Besides the consumer believe thats products with natural flavors are healthier, they're nutritionally is no different from those with artificial flavors. Another point it's that natural flavors may have more detrimental environmental consequences than artificial flavors, because to made them, there are forest clear-cutting and carbon emissions from transport.