spices adds  more flavors to food through the combination of aromatic compounds and heat sensations 

spices like cardamom helps to enhance the freshness and increase the smell of the food 

spices like chillies and black pepper helps to spice up the dish and red chilli helps to give the color to the food and make them look attractive and spicy and more tastier

spices can also be used to balance flavors in the dishes like garam masala gives the exposure to the food    

so there is no doubt without spices it is impossible to give exposure and taste to the food and that’s why india is known for its food because of its usage of spices and flavors

there are n number of spices in india we cant even know so the conclusion is just like that water is our necessity of life thats like spice is the necessity for indian food