Prior to the 20th century, management science focused on the challenges of the industrial economy. It tackled problems like getting more widgets manufactured by tracking the amount of time each worker spent on each task, then finding efficiencies. Workers were fungible and unspecialized, so it emphasized problem-solving at the level of the firm and of the manager.
When economic output shifted to Knowledge work, the field’s focus remained on the manager and the firm, since the individual workers had never mattered that much. This may be one reason why Core practices in knowledge work are often ad-hoc and We don’t know how to measure knowledge worker productivity.