Why does surrendering take an 80% majority?

I'm not a very good player, I know it. I contribute to one guy snowballing the hell out of the entire game as much as anyone else on my team does. When we're down 25 - 6 by fifteen minutes in, there's no point to continuing the match at all because it's already over. All that's left is to pointlessly throw yourself at the enemy so you can avoid getting reported for AFKing or giving up, which only makes the game take even longer.

But then there's the surrender option! A godsend if only it didn't go abysmally in practice, because the way it actually works is that two people whose pride can't handle surrendering in a video game can and will drag the game on ten, twenty minutes longer than it should for the other three. Taking the leave penalty would be preferable, or at least faster, but you can't even start a new game until the existing one is over with. Nothing like being punished for wanting to avoid wasting yours and everyone else's time longer than necessary.

Is there an actual reason why a majority isn't enough, that it has to be an 80% majority? Even if I'm caught on the bad end of that one too, at least it's because that was decided by as fair a vote as possible rather than a pair of trolls. I've never even seen an "early" surrender once, because that gives even more power to an even smaller minority, and is moot if anyone is AFK.