Why do humans have never-ending beard and hair growth, but no primates do?

I’ve been wondering about this: humans are unique in that our scalp hair and (for men) beard hair seem to grow continuously unless cut. Other primates, including our closest relatives, don’t have this feature. Their hair grows to a certain length and stops.

What’s the evolutionary purpose behind this? Is there a specific reason why humans evolved to have hair that keeps growing? And why didn’t this happen with other primates? It seems like a pretty inconvenient trait in the wild!

Would love to hear some insights or theories about this.