BEN - Why is it that women can't serve a mission until they're 21, yet men can serve when they're 19?

JOEL - I think it's just safer that way. With the women being older there might not be as much tendancy for the younger male elders to get too friendly with the more mature sister missionaries.
Also it gives the 19-21 year old women a little more time to get married to the slightly older men who are just coming back from their missions. If they don't get married by the time they are 21, and it doesn't seem likely they will, they might decide to go on a mission instead.