But that "problem" has to be equally true in any field of engineering you can care to mention.
Nobody goes back to raw materials for all needs, it's simply impossible. There's no reason it should be less so in software.
Many car companies chose to build their own engines, but not all of them do. I'm pretty sure that among those who do, they still don't manufacture all of their own engine components, or even the bolts used to assemble the engine, or the wires used to hook up the engine electronics, and so on.
Nobody goes back to raw materials for all needs, it's simply impossible. There's no reason it should be less so in software.
Many car companies chose to build their own engines, but not all of them do. I'm pretty sure that among those who do, they still don't manufacture all of their own engine components, or even the bolts used to assemble the engine, or the wires used to hook up the engine electronics, and so on.