Why are surfactants like POEA included in commercial Roundup products?

They lower surface tension to allow the herbicide to spread on leaves.

Surfactants, such as polyoxyethyleneamine (POEA), are chemical detergents added to herbicide formulations to improve their performance. Their primary role is to lower the surface tension of the liquid, which allows the herbicide to spread more effectively across the surface of plant leaves and adhere to them. While this maximizes the herbicidal impact on weeds, these surfactants can cause significant physical irritation, corrosive tissue damage, and systemic toxicity if human exposure occurs through ingestion or direct contact.