Why is the sexual dimorphism in humans so small?

Dimorphism is the difference between genders. Like male bulls have horns, male birds are colorful, and female spiders are much bigger then male spiders. But for humans, both genders aren't that much different, not even in size. Compare Brittney Griner and Tom Cruise. Seth Green and a female powerlifter. I was at Mcdonalds, and I saw a 5'5 flabby Mexican man, while next to him was a 6'0 African American woman who was more then 200 pounds. My Indian friend complains that many white women here are taller then him( and stronger).