Simple answer: Machinists measure & think in terms of thousandths. A scale marked in 10ths is readable & readily transfers a rough measure for the selection of stock. Most of my little 6" rule collection is in 16ths, so I have to convert. I don't mind as it helps me think & focus on the real numbers & memorizing the values of various fractions.
When I am working with wood (esp. dimensional lumber) I find fractions work best(16ths and 32nds).
When I work with metal, I'd rather use decimal inches.
Mostly because I cannot cut to the thou with my skill saw, and even if I could then humidity changes would negate that.
I thinks it's mostly about how accurate your work can be given the material.
Maybe also because my calipers and micometers are slanted towards decimals.
Sometimes I work in metric, if the need arises, but then I am usually converting the imperial measurements on the lathe and mill handwheel dials.
Engineering drafting scales are setup in 10ths or divisions of 10ths. Back in the day prior to satelites and after the 66 link chains surveying was done in10ths and hundredths. I like using 5 squares to the inch graph paper because it makes working with shop drawings easier. Worked in a housing subdivision project for a while, engineers set grades for sidewalks and push outs using inches and fractions because that is what the carpenters used. Later on got to using cubic yards and tons, makes for all kinds of useful conversions floating around in the head.
Have a good day