"This makes it easier to derive your own local metre without having to traipse over to Paris to check your metre rule against their 'standard' metre rule."
"Easier" for some value of easier. The kit required costs a bit more than the return business class fare to Paris from anywhere on Earth, with taxis and hotel bill added. The problem would come when you turned up and asked them to let you compare your rod to theirs. This is a case where actually using the primary reference (and transporting yours) is likely to affect its value.