Worm gears are used when huge equipment reductions are needed. It’s quite common for worm gears to have reductions of 20:1, and actually up to 300:1 or planetary gearbox greater.
Many worm gears have a fascinating property that no various other gear set has: the worm can certainly turn the gear, but the gear cannot turn the worm. That is because the angle on the worm is indeed shallow that when the apparatus attempts to spin it, the friction between your gear and the worm keeps the worm in place.
This feature is useful for machines such as conveyor systems, in which the locking feature can act as a brake for the conveyor when the motor is not turning. An added very interesting usage of worm gears is certainly in the Torsen differential, which is used on some high-performance cars and trucks.