Why is silica added to stevia?

Silica (just sand, really) is usually found in little packets packed along with new products to absorb moisture, keeping the pruduct dry. These packets usually have a label on them that say something like "don't consume." Well, some brands of stevia sweetener put the silica granules right in with the sweetener so that the sweetener components don't pick up moisture and get lumpy. That way it pours easily. But, there is no warning about consuming the silica. Presumably the FDA feels this is ok, but I'm not sure I like the idea of consuming sand. Some stevia brands don't have the silica.