Imagine having a garden. A nice, tiny little garden in front (or at the back) of your house. That must be quite a lot of work, taking care of it all the time. Removing the weeds, watering the plants, and so on, and so on. Depending on how much you like your garden you can spend any amount of time on it.
But some people don't have time for gardens at all. If they have one, they would rather not spend time on it. These people will put bricks, instead if plants, inside their garden. Bricks don't need maintenance, they don't tending. After placing them you need do nothing at all. But they are not very pretty, are they? Nobody wants to have a garden full of bricks.