Ever wonder why a consultant is more successful at accomplishing tasks than a regular full time employee? One word explains it “focus”. A consultant is usually brought in to perform a specific task, while a full time employee generally must multitask. Borrowing from the success of consulting, Agile prescribes dedicated full time resources. In addition to providing focus, having a single project prevents team members from having to context switch. Every time they need to switch projects they need to ramp down, get organized, and then ramp up. All of these activities cost them time, which is better spent completing project deliverables.
In addition to dedicated resources, Agile prescribes self-organizing teams. Think back over your past work assignments. How did you feel when you were forced to work on something that you had no interest in? Were you at your peak productivity level? Think back to a work assignment that you volunteered for. What was your motivation like then? Generally you have more of a vested interest in accomplishing a goal, in the least amount of time, with the highest quality possible when you get to sign up for it. People are happier and more motivated when they get to choose what they work on.