Age bias is a factor.
Ain't that the truth!
One of the things I used to love about working for engineer-managers is that you could never get an engineer to believe 2+2 can ever equal anything but 4.
Not anymore.
If you get an engineer that's 25 years old as opposed to 45, have him report to a "business" guy that's 50, and soon enough you'll have an engineer that can "compartmentalize" with the best of them.