There are some circumstances where it makes some sense. If the dog is a serious working dog, and long, floppy ears can be torn up by brush and such, it makes sense. Some tails should be docked if they are likely to be stepped on by heavy stock.
Never for cosmetic purposes, in fact the standards for some breeds are becoming more flexible, allowing for more natural looks.
Unfortunately, in some breeds that have always had docked tails (boxers come to mind) the tail configuration has not been taken into consideration while breeding, and many are born with tail deformities. It will be a much longer time before that can be corrected.