Raster charts are simply digital images of the paper charts. Vector charts are derived from the original paper charts. Initially that derivation was done by hand, now it is done by algorithms that take the depth data from the original charts and draw contours. The contours on the original paper charts were most likely drawn by hand by cartographic/hydrographic technicians who worked from soundings data AND noted taken by the hydrographic crew that generated the soundings. Basically, vector charts are more derivative than raster charts