In addition to its various flaws, the ‘vanilla’ OpenStreetMap lacks contour lines (or even basic relief shading) indeed. A big no-no for serious mapping needs.
However, I have to disagree with @nrg800’s statement about “precision data entry”: Google’s “satellite” (aerial) imagery can be quite inaccurate (cf. this thread), using it for pinpointing obs is all but ‘precise’.