For manual repairs it's certainly viable for some components, but it takes some care to not end up with tiny passives stuck to everything - if you literally just shake (or more, likely, scrape) everything off the board you'll get an absolute mess. And then you don't know if things end up damaged (or were damaged before, if you're talking about e-waste). It's not really something that works at scale. Even in the simplest case it's labour-intensive, so it's not economical in the vast majority of cases. Not for SoCs, certainly not for smaller things that cost singular cents, or less.

To reuse components in new products you'd have to harvest, clean off the old solder paste (reball in the case of BGAs), and sort everything, and then repackage them for pick-n-placing again. And if you're talking about more than just Apple reusing Apple products, there's also quite a lot of varieties of components.