Why the scale of an ohm meter is non linear?

V = I*R

R = V/I

If we fix the voltage at 1 then

R = I^-1

The change in the resistance scale is the derivative

R dr = I^-1 di

R dr = -I^-2

R dr = -1/(I^2)

Explanation:

The change in the resistance measurement decreases by the inverse of the current squared.