There is no one "Indian" culture. In the eastern Indian state of West Bengal, goat bone marrow is relished a lot, and fatty fish brain is relished and considered brain food.
Does this mean Ghee is generally not used in WB?
Sure there will be local variations due to a variety of factors - invasion of other cultures (islamic, christian, chinese etc) The Ghee thing does have its general influence in Indian culture.
Poisons in very low quantity are used to treat diseases. Could it be that Ayurveda uses milk to treat the imbalance of the "doshas"?
As a food, Ghee was used so very sparingly that it was almost not used at all. We cannot compare the quantities we consume today with those before the Dairy Revolution.
The writers of the Rgveda certainly were members of a pastoralist society, so they would have had a decent amount of dairy, if not quite the same quantities as today.
I know it will be considered pseudoscientific. I've used it and had positive results. What I am posting here is based on my own experience and observation from living here in India. I didn't come here advocating it. Just stating what I experienced. It may not always have a scientific basis in the modern sense.