Why is there a world's mission encouraging 5-man premades?

Let's be honest here: The majority of 5-man premade games are not good games. There's no matchmaking involved, so you likely have a vast skill difference within the same team. They exist, but they aren't something that should be encouraged, much less rewarded. Especially with such a silly goal as "destroy 2 towers within 15 seconds". I was honestly shocked when I saw this objective, and it still blows my mind that somebody at Riot thought they should encourage 5-man premades.