In India, why does the farming community use "Mixed crop-livestock farming system"?

All of the above.

In India, the farming community uses the mixed crop-livestock farming system — cattle, goats, fowl are the widely held species. Livestock production provides increased stability in income, food security, transport, fuel and nutrition for the family without disrupting other food-producing activities. Today, livestock sector alone provides alternate livelihood options to over 70 million small and marginal farmers including landless labourers. A significant number of women also find employment in the livestock sector