Dunno! The thought of sweetened yogurt grosses me out. In fact, all yogurt does, largely because of the name "yo-gurt". I can eat skyr if I mix it into other things or make labneh out of it.
(Following up on your edit)
Because it's more caloric than plain yogurt, for otherwise the same macro profile.
(Following up on your edit)
Because it's more caloric than plain yogurt, for otherwise the same macro profile.