For the answer to the question above, the use of a common measuring system makes it easier for people from different countries to communicate with each other. And also, the use of a common measuring system means a measurement in that unit has the same value anywhere in the world.
For more information,
1) It allows for international cooperation. This means that for example, you can understand and work with other people's results, you can cooperate with other people in production of goods (if you produce one part of something and they produce another) and you can repeat their experiments to see if their results were sound
2) It reduces errors caused by not rigorous measurement: a common measurement supports more exact specification of the measuring units, since many people work towards specifying it exactly.
