Write offs, PPP loans, deferrals, and all the other accounting tricks that the government carved out for the primary benefit of the wealthy are definitely a bigger loss of tax revenue. One guy writing off a personal vehicle for his personal business is probably what a busy restaurant makes in 4 months of cash purchases. Suppliers and distributors are also unlikely to deal with large volumes of cash just as a matter of practicality and risk, and the fact that you can’t have a functioning business with employees that need paychecks without going through banks which go through the government, unless you’re operating with an entirely under the table staff which is just begging for trouble.