Your analysis is faulty. This is not about cheap parts, it's about "being ridiculous."
This would be similar to making the entire dashboard a one--piece assembly, so that if just one indicator lamp, just one gauge, just one anything went bad, you have to rip out the entire and expensive dash and replace the entire assembly.
Putting the voltage regulator CIRCUIT inside the engine control computer is a really really stupid idea, and has cost some owners a LOT of money.
