The spring counteracts the weight of the door. In the event of motor or electricity failure a well adjusted spring/door will be easy to manually open. A direc

The spring counteracts the weight of the door. In the event of motor or electricity failure a well adjusted spring/door will be easy to manually open. A direct drive/worm gear would require an uncoupling mechanism and the ability to lift the full weight of the garage door overhead to get out. Attention is required when changing these, but they really don't pose that great of a risk. I've been present when one broke, and I've changed them myself. As noted by others - the spring stays contained by the metal shaft. They really aren't worth substituting with something that has more drawbacks when a spring's lifespan is on the order of decades.