... in fact it strikes some places a lot more than twice!
The map below shows the average number of lightning strikes per square kilometre per year.
I like this map because it involves looking at a pattern and, with a little lateral thinking, one can understand the processes that causes it.
Some places seem to get a lot more lightning than others and they are concentrated in between the tropics. Desert and polar regions do not get any lightning strikes at all. The areas with rainforests seem to get the most. So it is all to do with the places which are hot and wet, and experience more convection rainfall.
Although it seems obvious now, it is a very good diagram to start a discussion and revise rainfall.