Why cant you leave custom games

Today, i was playing with a friend and we found another person who wanted to play. So i accepted the game invite and realized it was a custom 3v3 on summoners rift so i went along to play with them (i only knew 1 person but apparently they all knew each other) then after a boring 5 minutes of all mid i wanted to quit. But the problem is that i couldn't because everyone has to leave. so after they played 30 mins i reconnected to see if the game was over and it didn't tell me. But no, the game was still going on and they were all messing around. I wanted to end the game but all they did was stand around doing nothing and dance at baron with the other team. I really wanted to play a match but i couldnt and the game would take too long because all they did was farm. The game lasted and hour long. An hour of my life was wasted i couldve been playing real matches but no i was trapped in the game wasting time and i couldnt surrender because of the 1/2 vote. In the end i just want to know why i cant leave these stupid games.