I see op's logic. How would you know when or if they did a poor job? Would it be after your audit, your guilty verdict, or the malpractice claim?
Just look at marketing and sales. It's basically a lottery...
Maybe can be changed to "Use your network to find..."
Hopefully referrals are a bit better than lottery
For any task you should be able to find information to teach yourself at least basic monitoring. If you can't get good at doing it, you can at least be reasonably good to judge if it's working.
Accountants, lawyers, and doctors all have associations who set professional standards they must abide by. They often also owe you a higher duty of care than someone in i.e. marketing or sales.
I still see where op is going, but accountants, lawyers, and doctors aren't the greatest counterexamples to use here.
Sure they are. There's plenty of variation in quality among people in those respective fields, just like every professional field.