Equal space dividers are useful for a variety of trades. Furniture and cabinet makers can use them to mark consistent intervals on workpieces without needing to do any math.
Seamsters, seamstresses and tailors use them as well. If you know where the top and bottom buttons on a garment need to be, marking out the ones in between is made easy with sewing gauges like these.
Luthiers and other string instrument manufacturers use them as gauges for string spacing nuts.
Those were the applications I knew about. But I was surprised to come across this one in the world of professional kitchens:
Turns out pasta and pastry chefs use them too, to cut dough into precise strips.