Sometimes you don't want the collective to be pulled down, e.g. in an engine failure in the hover or hover taxi.
Also, and critically I think with the R22, if the horn comes on due to overpitching, obviously a more gradual reduction in rotor RPM than a flat out engine failure, the throttle must be rolled on at the same time as the collective is lowered, otherwise the compensator will close the throttle and worsen the situation.
At first glance my feeling is the benefits of it might not outweigh the drawbacks.