This particular way of benchmarking gave employers a moral get-out clause. So, if they could demonstrate that employees were always in receipt of the minimum wage or its equivalent, they simply didn’t feel obliged to worry about anything else.
Salaries have been used to hide the fact that employees were being paid less than the minimum wage when things like the hours actually worked were calculated, making what appeared to be generous levels of pay turn out to be anything but.
By creating more and more laws in an attempt to cover every eventuality, our politicians just give the unscrupulous more and more loopholes to find.