If you asked me to find 2' 6" 17/32 on a tape measure or rule, I could point it out to you, straight off, even if the tape measure / rul was only marked in eighths of an inch.
What few people seem to grasp these days is that, pre-metric, nobody needed to know all of the old measurements; once you started work, you learnt the ones you used in your job and ignored the rest. So fencers, hedgers and ditchers, landscape gardeners, and dry stone wallers worked with rods and chains - because they were the handiest sized units for them to use in their job. Boatbuilders ignored rods and chains, because feet, inches and eighths of an inch were the handiest units of measure for them to work with. Woodworkers went down to quarter inch, eighths or sixteenths, depending on whether they were carpenters, joiners or cabinet makers, and so on.
Those different measurements weren't dreamed up by some academics - nor were they based on an incorrect measurement of the circumference of the Earth (as though anyone could calculate that accurately in the 18th century!). They were worked out on the job by working people, and the units chosen were PRACTICAL for their particular job. Also, the sub-divisions of units gave you a useful graduation of measurements, instead of the 'everything divided by ten, whether it fits or not' approach.