Some lunar craters are much larger than any known on Earth.
Obviously, any impacts on the ocean floor would not show up. Impacts are absent in Greenland and the Antarctic since these regions have been ice-covered over the last few million years. Impacts are also sparse in major tectonic belts as folding, faulting, etc. may have separated or obliterated them. Craters as such are not likely to survive the erosion that affects the crystalline shields of the world, although scars or remnants of large craters have been found there and a few young craters have been cut into the shields over the last 100 million years or so. The observed distribution is largely controlled by accessibility to favorable terrain on which the impacts are preserved and, to a lesser extent, on the desire by geoscientists in certain countries to search diligently for them.