Question

why did the pastoral nomads raise cattle?

Answer 1

Pastoral nomads raise cattle in order to earn money to support themselves for their livelihood. Cattle gives milk & milk gives a lot of dairy products which is needed in daily consumption. So, pastoral nomads raise cattle in regions which are less arable. They even raise cattle as a means of barter system i.e. in exchange for any other product in fair trade practices.

Answer 2

Pastoral nomads raise cattle because of two reasons. Cattle provides them milk, which they consume or sell. But, the animals also provide them with things like hide and fur, with which they either make articles for sale or trade as such for items they need for their sustenance.
Depending on the climatic condition, pastoral nomads the herded livestock cattle, yaks, sheep, goats, reindeer, horses, donkeys or camels, or a mixture of these.