I don't think it's really an issue considering everyone has the same options as everyone else. If you choose to stay after everyone else has left and you have no chance of winning while everyone else goes and does another FATE...that's your choice.

I do think leaving before it's finished sucks, but people should be able to choose how they spend their time earning their xp, and if that means bailing in the middle of a FATE to go work on another one, so be it. Not sure there's a fix that wouldn't just cause more problems, besides, I'd rather have SE spend their time working on other things that actually affect gameplay than try and fix this issue that really isn't hurting anyone.