It also prevents the a lot of speedruns. Imagine you can SR a dungeon and get that sweet extra bonus. That's bs. It doesn't prevent ALL the SRs, since you have to be lucky and be matched up with a group that: Knows how to SR. Is geared enough to SR. They're the perfect combination of classes for that. And, as the players mentioned, it promotes the commendation system. Queue, be nice and you will receive your reward and the feeling of doing a good job.