Do you put you dog in a crate or kennel?

My friend does but i don't like to do that to mine. my dog only using a crate and its huge and she's a mini pin when she has puppies and that's more for the puppies then her. Why use one if your dog is trained and don't get into stuff. I just don't get it. I don't think a dog is trained if it can't be trusted to be alone in the house. My friend says her dogs are trained but if she leaves them out they dump the trash and pee in the house. What do you think? If you do lock your dog up what happens if you don't?