Milk is synonymous with Punjab (the land of five rivers) and all milk products. Butter is an important cooking medium apart from being consumed raw along with the food. wikipedia
The Sikhs have a special relationship with milk. It is sacred. They have special ways they culture and prepare this prized raw ingredient. Every aspect of the process creating this sacred food is observed and respected intimately. Sikhs are vegetarians and believe very strongly in treating all beings with loving-kindness and respect. As a result they are very concerned about their cows wellbeing. They like to know the cows their milk comes from are taken care of and are not suffering — traditionally every family had a cow.