Early resistors were made in more or less arbitrary round numbers; a series might have 100, 125, 150, 200, 300, etc. Early power wirewound resistors, such as brown vitreous-enameled types, were made with a system of preferred values like some of those mentioned here. Resistors as manufactured are subject to a certain percentage tolerance, and it makes sense to manufacture values that correlate with the tolerance, so that the actual value of a resistor overlaps slightly with its neighbors. Wider spacing leaves gaps; narrower spacing increases manufacturing and inventory costs to provide resistors that are more or less interchangeable.
Early resistors were made in more or less arbitrary round numbers; a series might have 100 125 150 200 300 etc Early power wirewound resistors such as brown vitreous-enameled types were made with a system of preferred values like some of those mentioned here Resistors as manufactured are subject to a certain percentage tolerance and it makes sense to manufacture values that correlate with the tolerance so that the actual value of a resistor overlaps slightly with its neighbors Wider spacing leaves gaps; narrower spacing increases manufacturing and inventory costs to provide resistors that are more or less interchangeable