My dogs are all crate trained from little on up. Our boy is crated when we go away, simply because he gets into things he shouldn't. At one time he was chewing electrical cords, and I don't want to come home to a dead dog. He has a huge 3 ft by 3 ft puppy pen. The door is open all the time, and he goes out there and naps in his crate. I think sometimes he just wants to be left alone. That is his castle...
Our girl is loose at home when we are away, as she doesn't get in to anything dangerous to her.
I crate them when we leave them in the MH as they know their crates are their safe areas and they feel secure. It also keeps them from getting up and looking out the windows, which might precipitate barking. we never leave them very long at a time.
Last year our male had a vestibular incident and was hospitalized. He was calm in the hospital in the cage they had him in. I saw other dogs there who were really stressing from being crated. Digging at the door, squealing.... I like to keep my dogs accustomed to being crated because in a hospital situation, the dog is sick to start with and I hate seeing the ones who are stressed/panicked on top of being sick, from being crated.
I don't believe in over-crating a dog - I think it's abusive to have an animal just living in a cage. But there are times where it is a good thing for short periods of time.