How is 7% close to a rounding error? Especially when, in the case of landscaping, it is not a necessity and is almost completely for aesthetics[1]. If someone said they had money problems and it turns out they spend 7% of their income on makeup/barber visits/tanning salons, would you not point those out as possible expenses to reduce?

Just because residential usage is not the main source of the problem doesn't mean people should just not care about it at all. I'm not implying that everyone take 30 second showers. I just think it's important to be conscious of your water usage and reducing it when it makes sense. Addressing multiple sources of the problem simultaneously is possible. Also, sometimes it's possible that you're able to reduce the smaller portion more than the larger portion, so you should never focus only on the large numbers.

[1] Okay, neither are almonds, but I think you understand what I mean.