>I don't know how any of these environments promote apprenticeship which is slow, costly, and supports practices like long term investments in relationships between employer/employee.

While it's not completely either/or, this is a key point. When I first graduated, there were definitely companies that had formal 12-month or so training/internship/apprenticeship programs. We still have (paid at some level) summer interns, but extended rotations/on-boarding don't really exist.

And part of the reason is what makes sense for both employee and employer when 10 to 20 year employment tenure is pretty normal doesn't make sense if the new college hire will probably have moved on in a couple years.