Water supply would be the biggest concern when you're not hooked to a municipal water system... There's ways to make it work but everything costs money. Probably need some large head tanks to flood the system, etc. as a 15 gpm well pump isn't going to cut it in an effective time frame. At the end of the day, in the cost/benefit analysis I suspect most times it doesn't pencil. Insurance companies don't always favor sprinkler systems as much as one might think either.... as malfunctions and such can at times cause a lot of water damage... so sometimes bearing the risk of fire is the lesser evil.