Inside their city-states they might already have done it if there was a water shortage and major unrest was on the cards. Outside of their domain, they wouldn’t have done it (as opposed to couldn’t) - the power base for a SM is their city and the surrounding verdant belt. As the original campaign setting box states under the Templar class entry:
Templars never gain followers as do clerics. They never receive official approval to establish religious stronghold - a sorcerer-king’s life revolves around his one city and, while that may expand, he will never open branch areas that he cannot control.
As for PCs doing it…by definition PCs are the prime candidates for shaking up the world - the SMs are the status quo, the Veiled Alliance are city based and the Druids are too few and scattered. If my PCs want to start digging up the ground to find water I’ll let em. I might throw the ‘Dwarves of Hasken’ desert peril at them from DSE1 Dragon’s Crown (prospect for water, strike oil instead). Then again, as one of my players has a Psionic Artificer, maybe not. I’m not giving him ideas for internal combustion engines!