Because a lot of that was done in the factory meaning there was a cottage industry for a lot of it. Done in a normal factory and then sold on the side. Your salary was say $100 a month no matter what you did, you could make things on state time and then sell it and make double that(and still collect the salary). Same reason why vegetables bought from private peasant plots were amazing and kolkhoz stuff you bought in store was shit(when it was there at all lol).

Of course you had to pay some kick back to a manager or more likely give him a case of samogon.