Workers, productive workers saw little connection between production and reward. ( There were incentives, right from the beginning with Lenin and right through the end. The state did reward, but it was central planning rewarding, which suffers from what is called the Knowledge Problem. The well educated elites didn't, and could never, have enough knowledge to deliver rewards to the factory floor. When they delegated the gift giving, it was taken by intermediate graf/management. There is no way around this command economy problem. Hitler, the Soviets, Mao, even the Mafia and even the Army and General Motors all suffer from this command, large organizational problem.)
Some lectures on the Soviet Union from an economic view. Click on the one that seems most general/easiest first.