1. Researchers have shown that the community aspect of this kind of workout is important and effective. The fact that people train with others who has the same goals as theirs, drive more motivation.
2. People tend to workout better and harder on these types of classes because they don't want to be counted as the weak ones in the group. This way, there is a good competition between them, one that encourages them to train harder.
3. As we are social creatures, we tend to like social trainings better than being alone in a room full of strangers, like gyms.
4. You clients are more likely to continue to show up for the workouts since they feel more committed to the group.