Here's Bob Ragsdale's reasons to use a string loop:
"Eliminates arrow-falloff at full draw.
- Makes nocking point location less critical.
- No need to re-nock after a let-down.
- No serving wear from release aid contact.
- Assures easy one-handloading
- Releases can remain attached and ready to go.
- Eliminates gaps in serving from up pressure on nocking point.
- Controls peep sight rotation.
- Eliminates nock warping due to pinch at full draw.
- Allows release aids to be at an angle rather than only level.
- Makes shorter length bows easier to work with.
- Extends maximum available sight range area.
- Prevents arrow from sliding down the string during the shot.
- Prevents release aid rope slap with high cheek anchor.
- Improves shoulder alignment.
- Loop length can modify draw length of bow.
- Eliminates chin slap from inward swinging release aid ropes.
- Can be used with all non-rope release aids.
- Reduces string vibration noise."