Measurement of the utility frequency
The mains frequency can be measured at each socket-outlet. But it costs a great amount of time to build a precise measurement, to validate the recorded data, keep the the long-term operation with monitoring and replacing faulty equipment. So the idea behind the measurement of the mains frequency is, that a continuous measurement is cheaper than the construction of many individual measurements.
With the purchase of measured data the client receives the data immediately, and he saves time and budget compared to the development of measurement system. The operation of the long-term measuring is financed with the income from the sale of the measured data.