Answer:
Productivity for goods-producing tend to have a more simple variables for measurement. This might not be the case for service-providing occupations.
For goods producing occupation, productivity usually measured by two standards alone: The numbers of goods produced and the numbers of defect. A company will be considered to have good productivity if it has High number goods produced and the low defects.
For service-providing occupation, this measurement can be a bit more complicated.
Services usually depended on the type of costumers. A service that considered as 'satisfactory' by one costumers will not necessarily perceive the same way by the other customers. (For example, let's say that you work work as a barber and give 1 same hair style to two different customers. One customers might completely love your work while the other might completely hate it. Even if you're producing one same hair style )
This make measuring productivity for service industries become harder compared to manufacturing industry.