This is known as bikeshedding.

Something like turning off water is something anybody (also the campaign agency) can comprehend. Turning off water safes water, easy.

Now think about trying to reduce exhaust pollution, you can't see it, people don't know how much pollution is generated by a car, and most importantly: there is no easy solution to reduce it. Yes, you can ask people to leave their car at home and commute to work by bike, but that does not work for everybody and reduces comfort for most people.

The campaign agency could have done an awareness for exhaust pollution, but that would have been much harder to do, and probably they won't make much friends while doing so. Where as something easy as a water saving campaign will give that loads of goodwill.

Saving a liter or two of water two times a day for every person doesn’t seem like a bad start. It’s takes very low effort and you don’t lose any functionality, the water is literally just pouring down the drain.

Or am I missing some sort of sarcasm joke?

Many people feel an obligation to take care of the environment. If they make an effort to turn off the water when they're brushing their teeth and buy LED bulbs to replace their CFLs, maybe even upgrading their 2005 Corolla with a 2015 Prius, they'll feel like they've abundantly satisfied that obligation.

If they're (hypothetically) a commercial driver, spending the day at work driving around in an 1980s diesel truck, or installing golf course sprinkler systems, they'd still feel that they're an environmentally responsible person.

If the ad campaigns instead of suggesting toothbrushing habits informed the public of the disproportionate pollution caused by old trucks or vilified inefficient agricultural watering practices, that person might have a 100x more effective impact from their personal obligation if they advocate replacement of the truck or change agricultural practices. Also, consumers of these polluters might help encourage change by, say, preferring a waste disposal company that uses newer trucks or by changing consumption to eat peanuts grown with rainwater instead of desert-grown aquifer-fed California almonds.

You're framing this as if there can only ever be one initiative, and that saving water while brushing teeth was the wrong choice.

Realistically there could be a new initiative like that 1-5 times a decade. Society rarely behaves in the most optimal way, and as I said saving water is very low effort, though it might also be low impact. The real faillure not following up with more and better initiatives.

What if none of the available waste disposal companies are using newer trucks, are you supposed to call them every week like with congress people? And how is buying a bag of peanuts branded with some promise of ecological responsibility any different from saving water brushing their teeth? A single bag of peanuts from a different brand doesn't make any impact by it self and it only serves to make people feel like they've done their part adequately.

Not at all; just that of the possible initiatives one of the least effective options was chosen.

By analogy, if you were trying to help someone get out of debt, would you advocate they take unpaid time off work to walk along the roadside collecting cans for the deposit, or work overtime hours at $50/hr?

There's limited energy and funds available for these initiatives; by advocating ineffective ones more harm than good is done.

Saving water at home is nice but it's literally a drop in the bucket compared to the water wasted by inefficient agricultural practices. It won't make a difference one way or the other.

>It won't make a difference one way or the other

Goal is not to make a difference, it is to make you feel better for yourself.

And more importantly, distract everyone from the real perpetrators with special interests.

It's a very bad start because it effectively accomplishes nothing but waste the very limited bandwidth we have to convince the population to do anything. It also makes people feel like they're "doing their part", which isn't really true at all.

In some rural parts of Germany that are losing population that is actually not helpful at all. The sewer system is built for a certain amount of water and if less than that is used the utility company has to flush it with - more water.

So it really depends on the situation as well.