Opt-Out Sucks. Opt-In is superior.

Lets set the scene:
You're the party leader of a group of 4 people, 2 of which are AFK (apparently making food).
You and the only other active member in the party decide to do a group challenge in the interim.

But oh no! The two other AFK members were unable to decline the challenge, they were added to the challenge.

You and the only other active party member decide to keep doing the challenge, and end up waiting for another 10-15 minutes while the AFK people return.

Enter Opt-In:

You and the other active party member start a group challenge.
The two AFK people can't opt-in and now it's just you and the other active person.
Because it's you and the other active person, everyone in the party doesn't need to "attempt" or "finish" the challenge.

Congratulations. You have realised that Opt-Out sucks and is terrible.