He is comfortable and not forming bad or destructive habits. He also is not going to be confused by your reactions to bad behavior when you return. Remember, dogs do not have the reasoning humans do. When we return and see the garbage rooted through and then punish Puppy, chances are he will not realize what you are punishing him for. He may think you are punishing him for something completely different.
Crates also make house training easier.
Puppies and dogs generally will not soil their sleeping and eating area. Used with a consistent schedule, a crate can be your best ally with house training. Crates offer safety when traveling. A dog in a crate is far less likely to be injured in an accident. If crating while driving is not possible, at least train Puppy to lie quietly in the back seat or use a doggy seat belt available at many pet supply places.