I see a lot of exercise training videos, particularly for dead lifts that seem to recommend this.
The trainers will do several reps of the dead lift and upon completion of the last lift, they simply let go of the bar and let the weight drop to the floor. This seems to be more common with heavier weight.
Why drop the weight rather than make a controlled descent to the ground again? Does this do something to help increase performance?
Dropping weights is basically an acknowledgement that you either can't slowly lower the weights due to fatigue or that you want to avoid unnecessary risk of injury in slowly lowering them. It's only acceptable on a surface where this won't result in damage to the floor and weights, and it's more accepted with heavier weights and if you're clearly lifting to exhaustion.
Slamming the weights down is generally considered to be bad etiquette.
If your aim is to just improve your concentric portion, then it may be meaningful to not tire yourself by doing the eccentric part. However, there is no benefit to it. In addition, if you are doing deadlifts, I do not recommend you ever go to failure with that lift.
