Scrap is also cheaper and "greener." However........
A couple of years ago I audited a supplier who makes high-end grey metal castings. Very sophisticated operation, all the kit to analyze each pour in the ladle there next to the modern highly efficient furnaces. They won't use scrap in their melts as it's too-often contaminated with lead (and other heavy metals). The only material they use is bought-in pig iron of guaranteed (tested) quality plus other pure metals as additives to get the composition right, they do this rather than using scrap because it's the only way to reliably achieve the spec without contaminants.
Scrap is cheaper and "greener" so less finicky manufacturers like it. But unless they test each batch of steel/iron in the ladle, they won't pick up the contaminants from scrap before the metal is poured. But there's no real incentive to test in the ladle unless the end user tests each batch and can reject it, no foundry wants to bin a whole batch because the scrap they used contaminated it (sorry that's my cynical auditor streak showing through). Yes, more modern steel mills will test and will supply the "mill ticket" (certificate of analysis from the ladle) if asked..... but the buyer has to ask.
Even in UK, the Trading Standards and H&S regulatory functions are woefully underfunded these days, so you can imagine what it's like in less regulated parts of the world..... (that's globalization for you, a race to the bottom).
GC