I start a quest by clicking accept. I complete the steps of the quest. I get the reward I was told I'd get at the start of the quest by clicking accept at the end of the quest.
Players start the game with the same set of choices. They own the same user manuals. Their quests don't start without their knowledge. There's no such thing as a wrong quest. Even quests that some consider a waste of time have rewards. It's up to a player to decide whether the guaranteed reward is worth the effort that he or she will make. Quest givers don't care who a player is, who anyone else is, who s/he is, or about the state of gaming. There's no one with the reward who didn't do the quest.
There's a flip side, of course. The quest giver also doesn't usually care about the level of quality players achieve in completing the quest steps. It doesn't care if players get outside help.
Sometimes, quests are bugged. But players can file a support ticket when that happens, and eventually things are resolved. By things, I mostly mean rewards.
When I see a player with a shiny dagger, my first thought is Stabzor over there probably made a ridiculous amount of effort to get that Shiny Dagger of Stabbing...effort that I'm not especially willing to make. We choose to do different things with the time that we have. That's cool.
But, still. If I am willing to put in the work, I will get the reward. Most of the time, it's that simple.