The problem is that the linear transformation distorts the experimental error. These assumptions are usually not true with the transformed data. Since the assumptions of linear regression are violated, the results of linear regression are incorrect. The values derived from the slope and intercept of the regression line are not the most accurate determinations of the variables in the model. Considering all the time and effort you put into collecting data, you want to use the best possible analysis technique.
Nonlinear regression produces the most accurate results.
This figure shows the problem of transforming data. The right panel is a Scatchard plot of the same data. The solid curve on the left was determined by nonlinear regression. The solid line on the right shows how that same curve would look after a Scatchard transformation. The dotted line shows the linear regression fit of the transformed data.