It's absolutely mandatory that the developers of any game look at the consumer/player as a child. I'm not exaggerating at all on that comment, but I'm also not intending it to be offensive. A developer cannot trust the player base (as a whole) to behave accordingly. The proof of that comes from all around. Harassment, griefing, trolls, win-trading, hacking, complaints that someone is watching a cutscene, etc. If a developer actually truly expects the player base to behave like adults (mature and patient), then they're setting themselves up for a reality check rather fast.

That being said, it's a horrible idea to do this. While it may be a rather connecting event (in most cases) to be done between friends, the majority of the player base queues/joins groups solo. Just as you wouldn't want to trust that twitching homeless person with your money, you probably wouldn't want an unknown player controlling your reward.