Clay is used to line ponds in sandier areas. Once saturated, it acts as a barrier allowing very little water to pass through it. A planting hole in a clay soil can become a coffin. It acts like a bucket of water, drowning the roots of the plant. Clay is also used to make bricks.
Brick houses are strong.
They can last for centuries and withstand many an onslaught. Once upon a time, that story had a happy ending. When it comes to gardening, clay is more likely to be the beginning of a book with an unhappy ending. A typical example is a sodded lawn around a new home. Some builders spread a little topsoil on the ground first.