Public Goods

A Public Good is one that no-one can be excluded from using, and one person using it doesn’t stop others using it.
Public goods are under-provided by unregulated markets. That’s because public goods can’t be gatekept. Think clean air, street lamps. Some, like broadcast TV and radio, are provided by the market, paid for by advertising. But they are comparatively rare.
We wouldn’t pay an entry fee to enjoy clean air, because it’s all around us. But we do still want clean air! And we don’t want to have to buy a ticket. Hello dystopia.
So the government has to provide public goods that don’t occur naturally, like public parks and street lighting.
Our taxes pay for public goods so we can all reap the benefits.
Visual idea: Playground + hospital + bus icons.