Honestly, I do not believe that there is an actual need for a surrender!
If the enemy team are going to win, then they take the nexus, but you can at least try to defend and then push to give your team a chance for victory.
I have won a number of games in which a sneaky push of a lane whilst the enemies are focussed on trying to destroy the allied base, or simply just getting an ace and then pushing can allow a team to come back, however it seems as though people just want to give up when one inhibitor turret is destroyed, or after dying once send the message "surr at 20", it is still possible to win, but having the surrender button appears as an easier option.
If there was no surrender option, in my opinion, teamwork would increase, as well as player's abilities to play the game well and become better, and in turn this would reduce the amount of people harassing players in games calling them "NOOBS" and telling them to "delete the game" because they 'can't play', 'are unskilled' or some other slur in game, when honestly, the player will not improve if you do not help them! If you are fine will calling someone noob then you clearly must be the absolute best at the game, so why do you not help them instead? Tell them what items to buy for their champion, what order to max their abilities, tips on how to play their champion, and tips against the enemy champion. Otherwise you are never going to get a game in which at least one player is not a so called 'noob'. The games in which the word 'noob' never appears (1 in a million) are the games that are most enjoyable. Anyway, I've strayed off topic a bit, going into more detail, but I definitely believe the removal of the surrender button would be a good thing to do. What do you think?