1. In both China, and the Soviet Union, nobody would guarantee you a job. You had to find one for yourself. [1]

2. But because of funny accounting (When your business can operate at a loss, it's easy to overhire), there was no shortage of jobs. There was a shortage of good jobs.

3. Food and housing (At least in the USSR) was very heavily subsidized.

[1] Unless you were a collectivized rural farmer, in which case, you had very few options for leaving the kolhoz. It was shitty, hard work, that paid very little, and most of the people doing it, as well as their children had few alternatives.