Why use collars on bars?
Using collars keeps your weight plates close and snug to the shoulder of the bar and helps the load stay even. Without collars, weights are free to slide off the bar or to the edge of the bar. If the plates are not in the same place the load will be uneven.
This can also cause one side of the weights to fall off and cause the other side to head straight to the floor. This can cause injuries and it can damage equipment. Even if you are lifting within a time frame and trying to change weights fast because of that time frame, collars are still safer to use than thinking you can lift a lot of weight without them.
Collars also help the weight stay on the bar for if you have to bail the weight during the lift because it is too heavy. If you didn’t have collars on the bar while bailing it then the weight could either fall off the bar during the bail and cause damage to you or the equipment, or the bail could not go as planned.
Collars are also effective for when we are doing faster sets so we can touch and go and we don’t have to worry about weights flying all over the place while trying to workout. Collars are useful for heavy weights to make sure we are lifting safely and for fast sets so our weights don’t fall off.