Panther140: there's no such thing as a free market.
Governments have the right, and indeed the responsibility, to regulate and tax in the public interest.
In a totally free market, anyone who thought they were an engineer could design anything that customers would buy, for any fees. The insurance industry would be there to compensate the victims, assuming governments required people to carry insurance. If not, people would just die and others would go bankrupt and move on. Who would be there to protect innocent bystanders from being injured in the first place? Most societies long ago moved beyond merely offering people "blood money" for permanent injury- they want some reasonable assurance of injury protection in the first place.
If you concede licensure and regulation, i.e. codes and standards, engineering licenses etc., then all you're saying is that anyone is free to enter the workforce, apply for a license when required, and work for whatever money- or none- that they feel is fair compensation. Aside from minimum wage laws, we're pretty much already there.
The reality in a modern society is a little more complex. Right now we're beavering away at solving the perceived problems of the 1950s in the labour market. Whereas once it was a great achievement to just get a university degree- especially one in a regulated profession- now it's not at all rare. Educational attainment in Canada as an example is so high now that the bachelor's degree has taken the place of a high school education as a minimum required education for employment. We're cranking out so many engineers in Canada that only 30% of engineering graduates here work as engineers or engineering managers. When you consider that education here is still substantially publicly funded. With so many fresh grads unable to gain entry to their chosen profession, it's natural that many will reach around- for a while- for innovative ways to gain experience without requiring compensation for it. Does "free" represent fair value for the services rendered by these interns? In our view, the answer is definitely NO. We pay our interns, always have, and always will, because we find it unethical to de-value the services of our future generation. Our interns' pay is a fraction of an engineers' starting salary, which increases with experience, and that's fair value. And yes, we make money from their services- but even more important than that to us as a business, the pool of past co-op students is our natural recruitment channel. This greatly diminishes the importance of the (near useless) interview process, which is basically the equivalent to a phone call plus two dates and hour or two long prior to marriage- not a reliable strategy!