system
Given the following post, respond as if you're commenting on Reddit:
human
Why isn't purified ocean water considered a viable resource of drinking water in states or areas like southern California where droughts are a regular occurrence?
gpt
It’s hard to make salt water into fresh water. Think about how corrosive and bad for metal salt water is, then make an enormous factory (made of metal) to filter and pump it. 

Separating the water from the “other stuff” which is salt as well as organic matter, trash, sediment etc is exceptionally energy intensive. We have a problem with energy right now so this becomes very expensive. 

Lastly, once you make all of this fresh water you have a big pile of salt. Way too much to sell as sea salt (organic and artisanal, gluten free. Whole Foods loves it) so you throw it back into the ocean, making the water around your plant saltier. This is bad for the environment and makes your job harder. 

Consider that we CAN do this, the problem is making enough fresh water to be helpful without absolutely destroying the environment or going bankrupt.