When playing an MMORPG, there are two main ways of leveling up: doing quests and grinding skills. Generally quests and grinding line up to some degree, but not in RuneScape.
Quests in RS involve talking to a person of interest somewhere in the world and asking if they need help. This will initiate a sequence of tasks to complete around the world until the storyline is resolved, after which the player will receive experience in various skills that were used. Certain levels of various skills are often required to complete a quest, as the tasks can involve using the player’s skills to solve a problem. The number of repetitions of the skill to complete the task is relatively low, but it often takes many repetitions to get the skill to the level that allows the player to even begin to perform the task. In this way, these skill requirements become goals or milestones in a player’s practice/training in order to complete these tasks for the quest. I would first need to achieve some proficiency in mining in order to extract the ore needed to help a knight forge a sword out of a particular metal.
In a way, quests are very similar to projects in the real world. Projects and quests both involve a variety of skills, and those skills require a certain level of mastery to complete. There are some situations where mindlessly grinding is more efficient but often doing projects (questing) is the fastest way to improve. Even when grinding is faster, completing projects breaks down the grind and gives tangible milestones for a real goal with meaningful impacts. This fuels us with motivation to train ourselves to hit these milestones. The increase in stakes can alter our typical reward function and help in training intuition. It gives us excited accountability.
In RS, the XP you get from doing a quest is often much higher than if you grinded that skill repeatedly; just like if you actually apply a skill to a project you’ll learn more from the context and from having to finish things from end-to-end. This is similar to how enabling environments require a goal. Completing the quest could also give interesting perks from helping particular groups of people that can help with the related skills in the long run.