Notice there might be a good reason to kill a rated game. For example the game might be unplayable due to network lag or the game taking too long. The players could accept a draw (vote) which wouldn't change the rating (#2512). Otherwise the lagger / absent party would be declared to be defeated.
Also if we only punish the host for quitting a rated game, then the clients can still quit to avoid a rating (and we shouldn't trust the host if he says that that guy left).
Instead we could limit rated games to games hosted by Wfg on a dedicated server using #3556. The server would be able to verify who goes absent or lagged too much for too long and inform the lobby bot to adapt the rating.