Mostly the desert and the lack of fresh rainwater. Much of it comes from canals which siphon from lakes and rivers that are hundreds of miles away or more.

Comes out of the tap with a sulfur smell usually and is usually cloudy before it clears up. Every house has some sort of reverse osmosis or 3 stage cleaning system cause the water is so hard.

Had to replace my shower heads every 2 yrs when I lived there

I will challenge that with AZ water. Truly the worst tap water in the nation lol.