There is a lot more to swimming pool cleaning than skimming leaves and brushing your pool walls. Everyone can brush their teeth, but there are many more components to maintaining a beautiful smile and bite. Swimming pool cleaning has many components as well.
You need to skim leaves, brush the pool wall, tile, and steps, vacuum the bottom, test and balance your chemicals, keep your pool equipment maintained and performing well, backwash your filter, kill algae, etc. You also need to perform these tasks on a weekly basis which means there is little room for error.