They can enjoy the game without asking people to leave a strike. If they were waiting for their third, why go into the strike early and ask someone who solod an entire strike up to the boss to leave. Even if I want to farm with a buddy, I have never and will never ask someone else to leave a strike either at the beginning or the end. It is wrong to do. The person who is solo has just as much of a right to be there as the group does.