Depending on an archer's role in battle, such as being deployed in a harassing role, much like the Greek/Macedonian psiloi/toxotai who went out and fought other skirmishers before the main battle lines closed, I can imagine being able to move and shoot quickly would have been an advantage. I wonder how it would work with a heavy war bow from later periods? I've got a book on the longbow that speculates a lot of the shooting in battle against armored targets was at a relatively short range and at a flatter trajectory (which is why knights were described as bowing forward as if in a storm so they didn't take one through the eye slit), which allowed for aimed, powerful shots, but I'm guessing you'd still want to get off as many arrows as possible.
Whatever the reality was, I found this video interesting.
