I would reckon it's more likely due to lack of trying than project expediency. A C-suite sponsored mentorship directive would be a managerial innovation that few is any companies have tried.
A bad manager like the one you've described previously doesn't get a product done faster, cheaper and better. Quite the opposite actually.
You can find mentors, in the sense of people able to teach you things, and there are a lot of great people at Google, but there's nothing like what you described, and managers have unilateral power and the system seems to be described that way (project expediency, I assume).