Why do you require multiple people to remake?

I just lost a promo match because the jungler didnt connect, their duo said they werent coming back, and people still said no to a remake because "this is easy lol ill carry". I think that in a situation where you are going to be forced to fight an uphill battle, if one person doesn't want to have to have the i think 17% chance or whatever it is at winning a 4v5, they should be allowed to not have to do so, especially in ranked.