A very good question, but meteors do not all come in the same size. For an atmosphere like Venus's, it would take a large meteor to make it to the surface, but it is plausible that enough would survive over the last billion years to make the craters we see. Only the big craters would, of course, survive, but the real question is why there are so few craters and why they are randomly distributed. Normal erosion agents and tectonic activity would have obliterated craters in some areas making the distribution non-random. This is not seen. It is as though the entire crust scoured itself clean about 1 billion years ago, and has been completely inert since then. Some astronomers have proposed that every 750 million years, the crust turns itself inside out and re-hardens, allowing fresh craters to be recorded over the ensuing millions of years. This would account for the random distribution on the surface of the craters, and the fact that no very large, rare, craters exist.