Are toddler activities like swimming, music, art etc really necessary?

It is good for babies and toddlers to explore more activities in order to develop different parts of their muscles and senses. I don't find it necessary to send them to classes, but I would let them experiment with such activities at home first to gauge their interest and see if it's viable and worth it to send them for classes. Swimming is a very healthy way to bond as well and it's good exercise.