Borders for your landscaping are very important; they stop weeds and other plant life from invading your landscaping features and provide a nice contrast between the landscaping and your lawn. A border with a certain color can enhance the look of your landscaping and keep it anchored, allowing flowers and other features to stand out. While you have many options for landscaping border, you might note why concrete kerbing is the right choice versus rubber borders, gravel, and the like.
Concrete is very durable, more so than standard rubber or plastic pieces you might use for borders; if you were to run your lawnmower against one of those pieces, the border would probably chip and break very easily. However, concrete holds up well against a weed trimmer or edger or any other such equipment you might use on your lawn. It's more difficult for dogs to dig up concrete kerbing than cheaper border materials, so it may very well last for many years longer than any other option.
Keeping moisture in an area of landscaping is often very important, so that plant roots stay healthy and strong. Concrete kerbing can act as something of a small retainer wall for your landscaping features, if you have those borders poured deep enough to keep moisture in that area. Most other materials used for borders and edging are only large enough and set deep enough in the soil to keep them in place, not to actually retain moisture in that area. Using concrete means that you can create a small retainer wall around one area but then have the same type of design around another, without the same depth if it's not necessary. Your landscaping then has a uniform look while being protected from moisture loss where needed.
Concrete can be poured in any direction with any angle or curve you want, without compromising the integrity of the material. Trying to curve rubber or plastic edging can be difficult if not impossible. You can also have concrete painted, stamped, or stained to look like another material, including brick, stone, or something that matches your home's exterior. You typically don't have as many choices for styles and appearance with rubber or plastic or another such material. Using concrete kerbing allows you to create a look that is uniquely your own and then change that look later, if you have the kerbing repainted or stained again in the future.