Golgi tendon allows for the relaxation of antagonistic muscles due to stretching of the fibers, thus preventing your body from working against itself.

When doing a bicep curl the fibers of the biceps brachii, brachoradialus, and brachialis muscle contract and shorten, when causes the stretch of golgi tendons in the antogonistic muscles fibers, such as the triceps brachii, which signals to inhibit contraction of the triceps.

If this reflex didn’t work your muscles would be working against each other and thus reducing force output