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. Don't use linear regression just to avoid using nonlinear regression. Fitting curves with nonlinear regression is not difficult. Although it is usually inappropriate to analyze transformed data, it is often helpful to display data after a linear transform.
Many people find it easier to visually interpret transformed data.
Even if you analyze your data with nonlinear regression, it may make sense to display the results of a linear transform.