Why did ancient people on the Tibet-Quinghai Plateau herd yaks rather than grow crops?

Ancient people on the Tibet-Qinghai Plateau herded yaks primarily due to the region's harsh climate and high altitude, which made agriculture difficult. The cold temperatures, short growing seasons, and limited arable land were unfavorable for crop cultivation. Yaks, being well-adapted to the rugged terrain and capable of providing milk, meat, and transportation, offered a sustainable livelihood in this challenging environment. Herding yaks allowed these communities to thrive in a landscape where farming was not feasible.