Why do these requirements demand traceability in the international system of units, while I only work in France?

The purpose of traceability is to guarantee that measurement results can be compared, irrespective of the country where the measurements are made. Traceability can be guaranteed either by calling on accredited calibration laboratories (the LNE and associated laboratories inFrance) or, in certain cases, by calling on legal metrology organisations, which are also accredited in certain countries.