Information obtained from a contour map differs greatly from data taken randomly in the field.
Since contour map data is interpolated, the information may be less accurate than direct field data. The accuracy of the final surface model depends on both the quality of the contour map and the contour interval.
If you bring contour data into the drawing as points, then the points would not be very random. In steep areas, points would be close together. In flat areas, there is a greater distance between points on different contours. In both cases, the points along the contours are generally close together. Therefore, information taken from contours does not make effective random point data, and random data points generate the best triangulation.