I haven’t taken any physics since like highschool but basically bugs are very small and weigh very little compared to humans that are very large, meaty and heavy.
Insects also have exoskeletons which add a bit of protection.
Amount of mass goes up faster than amount of surface area does. Bugs just don’t fall very fast most of the time, plus they have an exoskeleton and are designed not to take damage from falling.
Though I have seen a fat garden spider, one of the huge yellow-and-black orb weavers, that fell out of its web and died because it was full of eggs and therefore too heavy.