Engineers are expected to take responsibility for themselves. They are, after all, "fully formed adults" (in Patty's parlance). And honestly it's not that hard to figure out which skills are useful to the work around you.

Netflix has traditionally only hired very senior engineers. Mentoring, at least technical, isn't seen as necessary for these people. Further, if an engineer thinks mentoring would help them, the onus is on them to seek it out.