This probably has to do with the fact that 'facebook' is the same in every language. Meaning that other popular items that may receive higher search volume are

This probably has to do with the fact that 'facebook' is the same in every language. Meaning that other popular items that may receive higher search volume are split among many different actual queries. The closest I could find to 'facebook' was 'youtube' which falls into the same category and comes in at just under half.