Think of whole spices as dried dormant seeds, leaves, bark and roots, full of aromatic oils with magical spice flavors within, just waiting to be released.
Whole spices have a longer shelf life than pre-packaged ground ones, retaining freshness until their intense flavor is extracted.
Which is why, even today, many Indian home-cooks will not contemplate having just store-bought ground spices in their kitchen, with the exception of turmeric and red chilies; both are best ground by a trusted spice merchant.