In at least one previous game you were able to initiate exercising. In VV5 it's just a random behavior they choose to do. So, it's not too useful, and would have been much more useful if those pesky untrained teenagers would do it sometime (I've never seen them do it).

It also seems to me that fixing huts is a slightly faster way to build skill than polishing the statue, because it seems like it takes less time to complete the fixing action, but it could be my imagination.