They know what's up.
Pennies are the white elephant of modern-day currency and are nothing but a burden to everyone who crosses their path. Pennies are so worthless that we have to trick people into picking them up off the street by pretending they're lucky. In case that's not clear, we aren't willing to pick up actual money because it's more trouble than it's worth.
We'll certainly leave pennies in the "take a penny, leave a penny" trays -- not out of interest in helping a future stranger but just to unload the worthless, unwanted hunk of metal on some other poor sap. Purses and coin jars are overflowing everywhere with useless, coppery garbage that is illegal to destroy.
An immortal doorstop.
The government itself is losing money minting pennies, spending 1.7 cents for every 1 cent coin they create.
Which leads to the question: Who on Earth is keeping the penny alive? The answer is Big Zinc. I'm not kidding. The main pro-penny advocacy group is sponsored primarily by Jarden Zinc, which makes about $48 million a year supplying raw coin materials to the U.S. government. They gave their organization a cutesy, groan-inducing name (Americans For Common Cents -- ugh) to make it sound like a homespun, grassroots sort of venture, but it looks like the same old story of a company trying to protect its golden (or zinc) goose.