To put aromatics at beginning or end of cooking?
Just like many other ingredients, when spices are added to a dish is a function of what effect you want them to have on the final dish.  If you want deep, well-integrated flavors, or even undertones, you add them early so the flavors meld into the product.  If you want a more pronounced flavor or an aroma, they are added at or near the end of cooking.  In addition, you can certainly do both, as the flavor and aroma can be enhanced by this double addition (at the beginning and at the end).  When these aromatic spices (and often alliums) are used, like in curries, they are heated in oil or ghee.  The oil is flavored, and this helps to carry the flavor of the aromatics throughout the product.  Spices and herbs also contain many volatile compounds, which will be lost with heat and time.  In this case, a last minute addition, just before serving, is the best approach.

"What do they know that we don't?"  Well, "they" know the final result that they are trying to achieve, and how ingredients behave at various points in the cooking process.  The end goal is a well-integrated dish.