As a matter of semantics, buildings, machinery, tools, computers, food, fuel, etc. aren't generally considered part of a manufacturer's supply chain (unless it's in the business of making those things, of course) - even though, as you correctly point out, they're just as necessary as the materials themselves. The "links" in the supply chain typically refer to the steps in going from raw materials to finished product - so a cotton farm would be one link in that company's supply chain, then the factory that turns that cotton into textiles, then the factory that turns those textiles into articles of clothing, then the retailer that sells those articles of clothing.
Semantics aside, I think it makes sense to focus on the labor standards around the harvesting of raw materials and the manufacture of the products themselves for two reasons. First, I assume that they're the most labor-intensive parts of the process. If you amortize the amount of labor needed to make a computer or industrial sewing machine (including mining the raw materials) over the number of articles of clothing they can be used to make, I bet the amount of labor used per end product is pretty negligible. Obviously I'd prefer if that labor isn't done by enslaved people, but I'd rather prioritize the more labor-intensive components. Second, my impression is that the clothing industry is distinctly awful with respect to the amount of slavery and sweatshop labor in its supply chains. Lots of the building materials, machinery, and food, and fuel used and consumed in the US are produced in the US to begin with. Food production in developing countries often uses slave labor, but at least there are reasonably effective ways to avoid that (e.g. by buying fair trade products). I'm sure the mining of raw materials for US-manufactured equipment often relies on slave labor, but again, I'd expect that's far less labor-intensive than food or textile production. Conversely, manufacturing clothing is highly labor-intensive, and when that labor occurs outside the US or EU it's pretty much guaranteed to be performed by people who are literally or effectively enslaved.
I'd love to support businesses whose operations are completely slavery-free, But I'm not sure that's even possible at this point - slave owners seem to have a monopoly on semiconductor manufacturing, for example. And I worry that too many people let perfect be the enemy of good, and throw up their hands and do nothing as a result.
Semantics aside, I think it makes sense to focus on the labor standards around the harvesting of raw materials and the manufacture of the products themselves for two reasons. First, I assume that they're the most labor-intensive parts of the process. If you amortize the amount of labor needed to make a computer or industrial sewing machine (including mining the raw materials) over the number of articles of clothing they can be used to make, I bet the amount of labor used per end product is pretty negligible. Obviously I'd prefer if that labor isn't done by enslaved people, but I'd rather prioritize the more labor-intensive components. Second, my impression is that the clothing industry is distinctly awful with respect to the amount of slavery and sweatshop labor in its supply chains. Lots of the building materials, machinery, and food, and fuel used and consumed in the US are produced in the US to begin with. Food production in developing countries often uses slave labor, but at least there are reasonably effective ways to avoid that (e.g. by buying fair trade products). I'm sure the mining of raw materials for US-manufactured equipment often relies on slave labor, but again, I'd expect that's far less labor-intensive than food or textile production. Conversely, manufacturing clothing is highly labor-intensive, and when that labor occurs outside the US or EU it's pretty much guaranteed to be performed by people who are literally or effectively enslaved.
I'd love to support businesses whose operations are completely slavery-free, But I'm not sure that's even possible at this point - slave owners seem to have a monopoly on semiconductor manufacturing, for example. And I worry that too many people let perfect be the enemy of good, and throw up their hands and do nothing as a result.