The world is regulated by standards. We use standard in our life every day; from your cell phone to the water in your tap to the electricity in your home. Road signs, engines, accounting, printing, packaging, food, just about anything that you can think of. (Think ISO, SABS, ICASA, IEEE etc).
The air you put into your tires is measured. The fuel you put into your car has to conform to certified specifications. A doctor has to use a calibrated syringe to inject the right volume of medication. All instruments of weight or measurement have to be calibrated to ensure that the correct standards are being followed.

If you use non-calibrated instruments, you may have the incorrect tire pressure or your car may not perform due to the incorrect fuel. Or you may die because the doctor injected the wrong dose! So many things can go wrong if we do not follow the rules.

Why then would you use an unqualified guy to do work that can have very damaging consequences to your family or business?
I have learnt to pay what is due as the consequences for not following the rules are always more expensive!