Beet harvesting is a complicated type of harvesting in that before you can actually harvest the beets with a harvester you need to use a Haulm Topper to slice the tops off of the beets, and only THEN can you use the Beet Harvester to harvest the beets.
While Beets will likely end up being one of the last crop/fruit types that you incorporate into your farming adventure, mostly due to the extra and special kit required, it is a crop and farming experience you should try to have and experience at least once in your farmer life!