What's The Point of Goosebumps For Humans?

Goosebumps are a vestigial reflex, meaning they are a leftover from our evolutionary ancestors. In furry mammals, the small muscles (arrector pili) attached to hair follicles contract, making the fur stand on end. This trapped a layer of air, providing insulation, and also made the animal appear larger and more threatening to predators. Humans have mostly lost their body fur, so while the reflex remains, the insulation effect is negligible. They now primarily appear in response to cold or strong emotions (like fear or awe) as an evolutionary echo.