TruShot touched upon the release aid and wear issues.

However, the loop makes for much easier tuning and better nock travel as well. There is virtually no upward pressure on the arrow nock, whick makes for a smoother release. On the short bows we have today that is extremely critical.

Becuase of that it makes arrow spine selection MUCH less critical.

It also reduces torque and allows one to let down with no fear of the arrow coming off the string.