What mydog says - the objector the exercise is to let the dog realise that the crate is its own personal space - somewhere it can retreat if family life is getting on top of it, the kids are getting on its wick, it just feels under the weather, or just wants a kip in peace.
It serves to keep a puppy safe during the chewing everything stage, when the dog could destroy expensive stuff, or (WORSE!) swallow harmful objects or gnaw through a wire and electrocute itself.
It is NOT somewhere to cage your dog, or leave him locked up for hours and hours. You may shut the dog in for an hour while you go to the shops, but you open the door and let him out for a wee and a cuddle as soon as you come back, and leave him out - the choice to go into the crate is the dog's.
As owner, it is YOUR responsibility to teach, socialise and show the dog how to be part of the family.
Too many dogs spend too many hours trapped in too small cages.
It's cruel. Always get the biggest cage / indoor kennel you can accommodate, and NEVER use a kennel in which the dog cannot stand or sit, or lie at full stretch. They are a tool, not a punishment.