Transport and a personal vehicle are two different things, go to any country outside the US, car ownership is reserved for the upper classes globally.

And access to transport was widely available to the overwhelming majority of the population through trains, trams, buses and trolleybuses. Even if your American mind can’t comprehend this fact, owning a car isn’t the ultimate form of mobility, there are alternatives that are arguably better. City design was centered around walkability, density and public transit; metro systems were luxurious and a predicament all out of themselves, and housing being generally obtained through the worker’s union implied that workers usually lived in relative proximity to their workplaces.

The soviet economy was a developing, centrally planned economy, not running under the premise of overproduction and surplus but running under the premise of 5-year plans of production. There was full employment, and almost complete usage of the raw materials extracted and industrial goods produced. Making twice as many cars, implied removing all of that labor and those resources from another sector of the economy. When the premise isn’t to “make money selling cars to rich people”, but to “grant adequate material conditions and welfare to every citizen”, you have to make decisions like that. More cars could have implied, for example, fewer hospital beds or fewer trams, but my point is that making more private cars would have NECESSARILY meant making less of something else of which there’s also no surplus (because the premise of the USSR was the non-existence of surplus). It’s very easy to have surpluses in a capitalist economy when you don’t care about 80% of the population not having access to the goods and services available, when you want everyone to have access it’s a different story.