They're just doing what they were told

There’s been a problem at my office with people putting all manner of things down the drain in the kitchenette. There is a garbage disposal, but there are limits to what it can handle. (Coffee grounds and coffee stirrers are high on the list of things the disposal can’t handle.) The result is that the drain has been clogged on several occasions and the plumbing bills have been significant.
In an effort to put an end to the problem, the facilities management group put up a sign asking people to “Please Do Not throw coffee grounds and/or stirrers into the garbage disposal.”
This didn’t solve the problem. If anything, the problem of coffee stirrers being thrown into the disposal actually became more frequent. That’s when a couple of us noticed something funny about the sign.
It turns out that the woman who put the sign up put it eye level. She’s also five feet tall. Most of the rest of us are taller, so our eye level is a bit higher than hers.
Oops!  The sign's just a little too high...
My theory is that the people who’ve been throwing coffee stirrers into the garbage disposal are just following directions. At least, that’s how they see it.