You might have long grassy wilder areas that you want to 'improve' visually with some flowering plants. This can be difficult if you don't know what works well, resulting in many losses.
Techniques have been proven to work with a range of species. This is an effective way of dealing with that wildflower meadow that has reverted to a plant community dominated by vigorous grasses. If you don't want the hassle of starting from scratch why not improve it with planting.