sorry, but this is another population density map
Note the large number of strikes in the Sahara desert (and Antarctica, as someone else noted).
There are at least two things going on here, probably more:
1) Population density 2) Ease of finding the meteorite or crater (this is easier in barren areas with relatively homogeneous terrain, like the desert and Antartica).
In fact, the effects of 2) are reinforced even more, since my guess is that many, if not the majority of these findings were by scientific studies/surveys (note that they typically list the date found, not the date it occured). And since no one likes wasting their time, they would obviously pick areas where it would be easiest to find evidence.
One would expect the true distribution to be extremely uniform, right?
However, there could be a favoured plane of arrival, like the solar system plane, and with a circular cross section of the Earth I'd expect less debris/area near the poles. (I don't know this, I'm just extrapolating from what I actually know.)
As it turns out, Antarctica is a very productive place to look for meteorites, first because there isn't really a preferred geographical zone for meteorite impacts, and second because of the large, empty ice fields, against which newly fallen meteorites stand out.
One of the most famous meteorite finds of all time, ALH84001, was located by simply driving across the Antarctica landscape and watching for dark objects.
;)