Because entrenched, and exceptionally wealthy interests. Reading about how about in CA there are tons of Colorado River fed foreign owned farms growing alfalfa to export to the middle east is the definition of capitalist success…the profit of a commodity has been made the most efficient; acquired cheaply for something otherwise impossible with international arbitrage as the medium.

Every time someone asks people in the southwest to take shorter showers show them this: https://www.foodandwaterwatch.org/2022/02/24/california-water/