The question may have been the scaling of line widths in a linear fashion while using vector images, which isn't that pleasing to the eye, compared to a hand crafted raster with more eye pleasing line width for a give size/resolution. May for aesthetic reasons line widths may require to be scaling in a nonlinear way?

Scaled vectors will have mathematically correct line widths, but to a human perception the line may appear to thick/thin for the image size, than which a raster artist would have used if they were creating a native raster of that size.