Engaging in some sports activities is a necessity if we are homeschooling not just to get them out of the home regularly but to relax ourselves, it is a difficult task to keep a kid engaged all the time. Even though my kid never gets bored of free play, it is difficult to find playmates all days and get ourselves involved in play every time they ask for it.
We enrolled him in skating classes when he was 4 years old and after a few months, switched to tennis because he was not interested in skating anymore:). These one hour sports sessions are perfect for us, he mingles with other kids, follows instruction from other adult, and learns all about team work, competition and supporting others.
I guess getting our homeschoolers engaged in some activity for one hour out of home is almost a necessity.