It’s called companies saving $ on labor. Resource, human resource, or labor allocation are probably close terms. But when it comes to explaining it diplomatically, I think cost savings is the best way, especially if you’re explaining it to management.
If you’re paid 50/hr and an assistant is paid 15/hr, the company saves $18 for an assistant to spend 30 minutes making photo copies rather than you. You now get 30 extra minutes on x project, which will make the company more money, further increasing the company’s profits through smart labor allocation.