Because it allows them to breathe and function.
They can accidentally catch dolphins, turtles, even orcas. Greenpeace is actively trying to get them banned.
Answer:
Visible light, ultraviolet light and infrared light
The troposphere is shallowest or narrowest at the poles, and deepest or thickest at the equator. At the geographic North and South Poles, the troposphere reaches only 4 miles high, while at the equator, it extends nearly 12 miles high.
