Ensuring that each colony has the right amount of space available in their hive year-round helps to ensure a healthy and productive colony. The bee colony is made up of the lowest number of individuals during the winter. During the spring the colony grows and the beekeeper needs to respond to this increase of number of bees. If the colony does not have sufficient space they will likely swarm, which is not really in the interest of the beekeeper. The bees begin to collect nectar and pollen and need room for storage of surplus food, i.e. honey. As a beekeeper interested in harvesting honey, one wants to give enough space to the colony to stimulate their growth and collection of nectar and pollen, while keeping the hive small enough to ensure the right microclimate. A huge hive would not be suitable due to the bees having trouble regulating for example the brood area temperature.
Swarming also has the function of ensuring that the bees inhabit a new hive, with a minimum of disease pressure. In a certain sense they are leaving an old rundown house and building a new clean one. When we as beekeepers try to influence them not to swarm, we need to also take into account that they can in a certain sense renovate the old combs. By giving them space and new combs, potentially with new wax foundations, we are encouraging this renovation of the hive.