Here's why:

* The troposphere is the lowest layer of the atmosphere. It's where we live, and it's where most of the atmospheric mass is concentrated.

* The troposphere contains most of the Earth's water vapor. Water vapor is essential for clouds, precipitation, and many other weather phenomena.

* The troposphere is the only layer where temperature decreases with altitude. This temperature gradient is crucial for driving atmospheric circulation and weather patterns.

Other layers of the atmosphere like the stratosphere, mesosphere, thermosphere, and exosphere are much higher and have different compositions and temperatures. While they have some influence on the Earth's climate, they don't directly contribute to the weather we experience on a daily basis.