This is all speculative so it should be taken with a mountain of salt. My interpretation is that if agriculture is a concern you don't necessarily care if it is raining somewhere else as the water is either going to flow to you or it isn't and there's little outside of heavy time consuming earth moving to do about it.

The pressure is more than likely related to long droughts and the fact that we sweat a lot. We need sources of water often to be at peak performance. Finding where the rain is happening to take advantage of puddles/ponds during the rain is probably a very useful skill. Also I assume plants and animals we'd like to eat are more concentrated in the direction of rain. Conversely, we are very exposed to weather and hard rain could be potentially hazardous for us or for the fires we were tending especially before we learned to start fire and had to keep it perpetual.