Bert, see my post above - how many furlongs make up one third of a mile? Or how many ounces make up one third of a pound? In both cases, you have fractions ...
If it were a twelve-bases system, I'd agree, but it is a 3 or 4 or 5.5 or 8 or 10 or 12 or 14 or 16 or 20 or ... based non-system.
s&r, you are contradicting yourself with Tradesmen already ignore metric rules which is why Kitchen units are given in millimetres, waist and collar sizes in centimetres; How can they ignore metric rules by using metric measures?