I've worked with the construction and trades industry for a long time - not as an employee, but as a vendor. I've talked to thousands of business owners. Most times at great length about their business and the industry.

The most common complaint for decades is a lack of employees. Nothing new here. But a lot of it is that the smaller companies don't have a concerted effort to attract talent. This is because most of the trades - plumbing, electricians, etc, are small companies of 2-10 employees. They are not advertising every week for new employees and keeping their resumes on hand for when someone quits their company. The larger companies, while still having problems recruiting, are able to keep their companies at 100 or 200 plumbers or electricans. Maybe the large companies are not growing as fast as they can, but they still have a lot of workers.

Most of the construction companies don't need to look for work at all. Because of the extreme shortage of employees, they all have way more work than they can do.

Child labor would put a dent in what construction companies need. Construction companies can't find 18-22 year olds to do the jobs. Why would a child do it? And not many parents would allow it, not even low-income households. Construction is dangerous as fuck.

Also, it is EXTREMELY physically demanding. So many people walk off the job after the very first day and just say "fuck it," just because of the physical demands - not even talking about accidents or safety. It's like being at the gym all day, working out for 8 hours straight, every day. Some construction workers must eat 8,000 calories per day to deal with the calorie burn. So you are eating 400% more food and you pay for that extra food, or your parents do.

You can see the danger of construction by looking at workers comp insurance rates for different industries. The workers comp rates are based on your payroll. Companies pay $x per $100 of payroll. So for instance, the average workers comp rate across all industries is $2.25 per $100 of payroll. So if your company's monthly payroll is $100,000 per month, then your workers comp payments will be $2,250 per month.

But it changes by job. So since office work is very little chance of injury, it costs 28 to 99 cents per $100 of payroll. Very inexpensive. An doctors office cotss $1.22 to $3.68 - maybe because a greater chance of getting a disease or moving an overweight patient or whatever - more risk than sitting at a desk, right? A garbage industry worker costs $6.19 to $23.63. Tree trimming and masonry is $12-$43. Carpentry is $15-$50. Roofing is one of the most expensive at $23-$87.

The more you have to pay in workers comp, the more dangerous the occupation is. Roofing is one of the highest, because people fall off roofs, off ladders, they carry heavy shingles and hurt their backs. So roofing companies are going to have to pay a lot more than office jobs.

FYI it goes by worker - an office admin person working in a roofing company still gets office worker comp rate.

But construction is extremely unsafe which you can see just by looking at workers comp costs.

One other thing that affects the cost of workers comp insurance is how many claims a company has. Just like auto insurance, the more accidents and traffic tickets you have, the more you will pay, until it is devastatingly high. It's the exact same with workers comp. If a company has a lot of workplace accidents, their rate skyrockets, sometimes until the company must go out of business. The reason for the rate increase is because the company has lax safety procedures, on the whole, right? Makes sense. Well, if you have 14-17 year olds, you're going to have a LOT more accidents because kids that age don't know what they are doing. And you put them in dangerous situations.

Think of it this way - if you are a homeowner, would you hire your next door neighbor's kid to help you with re-shingling your roof, or any other dangerous or mildly dangerous type of work??? Hell no. Why should we allow a company to do that? And even if you hire the neighbor kid to mow your lawn, that is vastly different than hiring a kid to commercially mow lawns for a business.
No way should anyone under 18-years-old be allowe to work in dangerous industries. Mandate that by federal law. If you want to get training for young workers, you can have them go out with estimators or foremen or do office work to understand and train them in the business. But no actual physical work as the tradesman.