That's why there is the joke about people from overseas not knowing how to tip.
It gets tricky for temps and contractors, so. If you are a temp, and employed by a third company lending you ut, that company can ask for Kurzarbeit. In agriculture and food processing, most of the work force are temps emplyed by sub-contractors. Thearetically, they are covered. In praxis, they are more often than not screwed. The sub-contractors sub-contractor is potentially ot evena german omany to begin with.
Shining light on this, is one of the few good things about Cocid-19, if you ask me.
But, paying employees cash only is much harder than it used to be. Many customers now only want to pay card. The tax office sees the card payments coming into your bank account, if you try to pay your employees cash it is easy for them to catch you. So, I think the number of workers actually hurt by that is relatively small.
COVID-19 has accelerated the transition from cash to card payment, because the health advice was to avoid cash payments (due to risk that cash may spread Coronavirus), and many businesses responded by refusing to accept cash entirely.
Guarantee you it is a huge number in Canada, and probably the U.S. as well. Tax fraud in food service, bars, and kitchens is the norm here in Ontario.