Remember that not all types of tortoises hibernate, Sulcatas, leopards, stars, Aldabras, etc.
Tortoises that do hibernate do so to survive winter. During that time of the year in their natural climate it is to cool for them to metabolize food and the food is often to scarce anyways. When spring comes it often triggers breeding instinct.
In captivity we provide optimum conditions for our torts so they do not need to survive cold temps and therefore it becomes the keepers preference.
Some feel it is more natural for them to do so and others enjoy the benefit of not needing to provide food through winter or providing an indoor enclosure during this time
I hope this helps you.