Oh, I dunno, maybe the intent is to save water? What water you say?:
Lawns, which have been especially singled out as water wasting culprits, are estimated to use about 40% to 60% of landscape irrigation in California, or just 3.5% to 5% of total statewide water use. Overall, landscape irrigation is estimated to account for about 50% of annual residential water consumption statewide. That amount varies widely from about 30% in many coastal communities to 60% or more in various inland suburban communities.
Given the drought California and the West is in, it seems reasonable to switch over to less thirsty gardens whenever possible. And to save water in the meantime by limiting watering.
No, not particularly defending growing thirsty crops like rice - which can be imported - either. It's not either or: turn both off, longer term. Water doesn't care for politics or fine legal analysis: it's either there in sufficient quantities. Or not.
nobody cares if their drinking water is 0.2 cents or 2 cents per gallon.
Average daily usage in the US is 300gallons/day, so I doubt $180/month is "nobody cares" territory, especially for poorer households who still need to shower and flush the loo.
And another way to think of water usage, per crop, at a national total level (I'll look for a per-acre data if I can find it).