And cars are frequently used to smuggle illegal goods.

All sorts of legitimate and useful things get used illegitimately.

Not systematically. Whereas the unions ...

Do you have a similar problem with cash-only businesses?

Not sure I follow how these two relate.

Cash-only and cash-intensive businesses are an incredibly easy and common vehicle for money laundering. The less customer information involved, the more effective. Such businesses are incredibly widespread and vital to organized crime, and their ease of operation in this manner is baked into their DNA.

Despite this, they too serve a useful function.

Sure some of them have, but their foundational democratic and working class structure makes it possible for them to have a progressive effect on society. By contrast, the corporations that they are in conflict with supported the Nazis and planned a coup against FDR because their foundational interests in a regimented, nationalist, power hungry, and elitist society were aligned.

https://newspunch.com/american-companies-nazi-germany/

https://en.wikipedia.org/wiki/Business_Plot

EDIT: to respond to comments below:

1. Union busting since the New Deal era resulted in one of the most oppressed working classes in the world. Hence, low union enrollment.

2. FDR saved capitalism. I'm not his biggest fan. I'm a socialist.

3. Serious money was offered during the business plot. It didn't come to fruition, but the danger was real. Corporations are the real power in America.

And yet the most unionized industry in the US (at like 75% of overall union membership) is white-collar federal employment.

There's nothing working class about that.

Working class are people that have to sell their labour to get income; capitalist class are those that live off capital income. (Dividends, rent, etc)

If someone is employed in a government organization, like the CDC or a secretary of the white house, and they don't have capital income then they are working class.