Why is there a train from Wuhan to Urumqi and there is no train from Urumqi to Wuhan?

The train tickets have been sold out. Wuhan, referred to as "Han" or "Jiangcheng" for short, is the capital of Hubei Province, a sub-provincial city, a megacity, a national central city and a central city in Central China. Urumqi, commonly known as Urumqi, formerly known as Dihua, is a prefecture-level city, capital and I-type city under the jurisdiction of Xinjiang Uygur Autonomous Region approved by the State Council, an important central city in northwest China and an international business center facing Central Asia and West Asia. There are trains from Wuhan to Urumqi, but there are no trains from Urumqi to Wuhan because the train tickets from Urumqi to Wuhan are sold out.