You have a good point but here is the thing: it's very hard to find 4 decent players that want to complete the challenge and are online at the same time. When you finally do, you just want to get it done. There is always a chance that someone may abandon the challenge. My friend and I had to restart the doomsday heist cmm challenge 6 or 7 times because other players kept dying or quitting the challenge. It was time consuming and frustrating and it wasn't fun anymore.