It should only take 2 votes to surrender.

The issue is I don't trust most people below gold (and even then) to properly assess what 'unwinnable' game states are. If it's below gold or so, then theres no such thing, since people are exceptionally bad at ending games and baron throws and similar are super common. If they're literally at your nexus towers at 20 minutes, sure surrender, but otherwise theres generally a chance the game will drag out until everyone is full build and/or whoever was carrying the opposing team gets cocky and tries to 1v5.

The number of games I've won after constantly denying the surrender vote is way higher than it should be, since people don't seem to understand relative champion scalings and other potential win conditions.

http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/2086588645/227541186?tab=overview Never surrender, look at the time the towers went down. There were no DC's in the match.