Haven't all the problems of the units long since been solved? Why is there any need for ever more precise measurements? (FAQ - Quantum)
Measurement is an integral part of modern science and technology. However, Metrology is a service discipline - responding to a perceived need for a particular measurement accuracy, either now or in the near future. That is, Science and Technology are the driving forces of accurate metrology.
The national measurement system is a pragmatic one, based on fitness for purpose. Units are realised with the best accuracy achievable on the day to meet the accuracy required on the day. However, science and technology move on to the next decimal place and so need more accurate units. Fortunately the improved science allows us to realize the units better to meet this demand. The ever increasing level of precision is driven by a need resulting from progress and not by the pursuit of measurement accuracy for its own sake.