In the US advertising is considered a business expense. So we equate it with investing in infrastructure or research, both of which reasonably would be subtracted from your revenue to determine your tax burden.
Payroll taxes are paid into social security as an insurance payment. It is a percentage of what you pay the employee. Some might say that it is part of the employees pay.
I don't know what that has to do with taxing marketing spend.
It's very dumb.