A friend of mine got a job straight out of university, and in the following years did biological, civil and automotive engineering.
Lawyering, in contrast, I believe is fairly specialised - in that it's not as easy to move around between different areas of law? Aslo, people will always complain there are too many lawyers, the economics of law aren't properly market-lead..
He stopped working with engineering about 15 years ago, because there was too many engineers, the pay was too low to be worth the effort and risk.
He recently resumed working with engineering, and unfortunately remembered why he had left in first place, he worked in a couple projects, and most of them had engineers getting pay less than senior construction workers, and companies frequently believed that hiring an engineer was just out of necessity because the law says so, and otherwise would build whatever they want without one.
This does had some very, very bad effects, like when an engineer-less construction company thought it was good idea to just demolish some pillars that were in the way of what they wanted to build, and managed to demolish two buildings and damage a third. (this happened in Rio de Janeiro... the person that asked to take down the pillars was the secretary, that looked at the project and concluded that by taking down the pillars they could fit more desks in the office they were furbishing...)
I would guess that most of what those fields have in common are their quantitative/mathematical nature. Would he have been just as fit for these roles with a degree in Math or Physics?
I think a math/physics degree might not have the particulars of structural design specifically.
Can there be too many people with 130+ IQs? Not sure about that.
Right now engineering degrees are valuable as intelligence proxies because the standards are less relaxed than other degrees. If everyone became an engineer this would no longer be the case.