Calm down. They're not jerks. They're not going out of their way to do anything malicious. Being able to only win one piece of gear per week, they simply just bow out when they get said weekly piece. Why do you think they should stick around for another 30+ minutes just so you have a better chance at winning the oil?

If SE wanted people to stick around until the end of ST, they'd increase the Soldiery reward to 75, instead of 15. That way, even if you won a piece of gear, it'd still be worth sticking it out until the end to get that nice chunk of Soldiery.