There are so many good reasons to crate train your dog and there is really no downside to it, so it is something we strongly urge our clients to do.
A crate should be a shelter and a safe haven for your dog. He/she should feel comfortable sleeping, resting or just "hanging out" in his crate. This also helps reduce "separation anxiety" - once a puppy/dog becomes comfortable in his crate, he feels secure knowing that you will come back to get him because you always have and it can keep him from constant whining or barking.
Safety is a huge issue as well. Traveling in a car, it is far safer for your dog to be confined in his crate. If you were to be in an accident, a loose dog can run into oncoming traffic in fear and confusion or dart off and be lost. In your home the crate not only protects your dog from small children who might be tempted to pull a tail or ear, but also keeps your dog from bothering others who might not be the dog lovers we are!
For a puppy, the crate also gives you both a much needed time out. To prevent a puppy from living a life of "no!" and constant reprimands, a little down time in his crate will give you both time to regain your patience in times of extreme puppy madness! Even dogs need their personal space and the crate is the best way to provide that. Anyone who has ever left a mischievous puppy or dog loose in their home or yard has been made aware of how incredibly destructive they can be!