In a former life I worked on 27 quickly-built kingdom hall sites. I got onto the 'plasterworks' team just as I turned 16, yippee!! Over the years we got the schedule pretty tight, in at 2:30 pm on Saturday afternoon, put the panels up. One guy on our team was a licensed electrician but never told the overseers because he knew that the work done there was highly dodgy and he didn't want any electrical fires being traced back to his ticket. Being young nimble and stupid I got the insulation job - fibre glass batts. Once we were issued itch-prevention suits but they were pretty ineffective in the 45C ceiling. I've heard that these days they restrict numbers on site and the only vacancies for sisters to flake around handing out cordial and cake are for the real hotties, and as I was genuinely working in my genuine steel-capped boots I always resented the girls who wore makeup on site. (To my credit, they're the ones who got married as soon as they'd finished school).
Legend has it that once, a non-witness construction professional was passing the site and was so impressed by the efficiency that he tried for months to negotiate to get our guys to build stuff for him. They quoted him as saying "you don't understand, I want to pay your people to build for me" and themselves as saying "No, you don't understand, these people only work for Jehovah". I guess it wouldn't have worked out for the guy if he'd also had to pay for qualified tradies in a currency other than guilt, babes and sandwiches. Or maybe the insurance would have pushed him over the line. I can't think of any other reason why WBTS hasn't ever tried to contract out their slave labour.