Dividing it by two gives you 3/8 rather than 9.5mm. Dividing it by 4 gives you 3/16 rather than 4.75mm. Both 3/8 and 3/16 are common sizes. You can drill holes cut grooves this size. You can use your 3/8 chisel to quickly find the centerline.
It's not like you can't do any of this with the metric system, but you'll either need to measure things more, or round things. Often rounding is fine, but to me it feels like a compromise that is born out of the measuring system; a compromise that isn't needed when using the imperial system.
It's not like you can't do any of this with the metric system, but you'll either need to measure things more, or round things. Often rounding is fine, but to me it feels like a compromise that is born out of the measuring system; a compromise that isn't needed when using the imperial system.