That's only true if you assume that in metric everything starts out as 1, 10 or 100 units. But that's not really what happens.
For example kitchen appliances and furniture basically works on multiples of 60cm: an oven or dishwasher fits in a 60cm slot, and accordingly your cabinets will be one appliance wide (60cm), two appliances wide (120cm) or half an appliance wide (30cm). And you will find that halfes, thirds, fourths or sixths of 60cm are easy to calculate. Lots of other furniture works on multiples of 80cm. Those don't have nice thirds, but halves, fourths, eights, sixteenths, doubles, triples, quadruples all work great.
And this happens not only in furniture but in everything. Having things 1.2, 1.5 or 1.6 of whatever unit you are measuring is common and allows you to have nice fractions. We just never write them as fractions. And honestly 45 + 7.5 is so much easier to do that 3/8th + 1/16th (of 120)