I am a strong advocate of crate training. Not only does it keep a dog, particularly a puppy, safe from hazards when unsupervised - but it benefits dogs when they need to stay at the vet overnight, or board someone unfamiliar. Potty training using the crate as a tool means less accidents, which helps puppies condition faster to using the bathroom outside only. Crates can be useful even in adulthood when we have guests who may have a challenging time greeting our dog friends, either because of fear, allergy, or some other condition that makes dogs greetings more complex.
Most people that I meet and work with only use a crate for when a puppy is small, and than ditch the tool when the dog is house trained well enough. Many of these dogs are "crate tolerant"- meaning that they will be crated, but could find it stressful- still make some noise, and are reluctant to enter when asked. Tolerating a crate is helpful - but what is better is having a fully crate trained dog!
Dogs that are fully crate trained are much less likely to bark or whine, even when their owners are in plain sight. Dogs that are fully trained do not rush doors or gates when being let out of their crates, and instead wait to be invited to exit. They enter the crate on command, with no resistance. Much more than that- they can often be found resting in a crate even when the door is open, or other sleeping options are available. As I write this, one of our dogs is on the couch, one is sleeping in a downstairs crate near the wood stove, and one is upstairs in the dog bedroom- a gated off area in our upstairs landing where they have beds and sleep overnight. This tells me a few things- 1. Our dogs are secure enough to rest out of sight, and know where they are allowed to do so. 2. Two of the three dogs have chosen crates or restricted smaller spaces to rest. They are comfortable and feel safe in their provided environment. While our dogs are not allowed to sleep in our bedroom (except for when it's so hot they need the air conditioning), they are not lacking in bonding with us. They are responsive, engaged, and incredibly trusting, with good recall and reliable listening skills. Many folks think that in order for their dogs to know they love them, they have to spend the majority of the time petting, cuddling, or sleeping next to their pet. While all of those things are wonderful ways to share affection with our dogs, it isn't the way in which we primarily bond.
My goal in crate training is create confidence and security in my dogs. I find that the crate also helps keep our self control training consistent. I want them to feel comfortable on their own, but not overwhelmed with the responsibility of a vast space. Rather, I want to provide a space for them where the only objective is to be calm, and quiet. We do this by super charging the crate itself with positive associations and rewards at first, and an unyielding commitment to silence being the only way puppy is allowed to exit unless they are communicating a bathroom need. Using a crate as a quiet reset can help when you are training around excitement issues such as greeting guests at the door, feeding times, visiting dogs or children. If you can create the right mindset for your dog around the crate- it can become a tool for the duration of their lives. I often times use it even when I'm doing training with my own pack, making them take turns working solo and being quietly observant in a crate. When we leave the house, our dogs, even the 7 year old, still stay crated. They are calmer this way, and it also helps us worry less that we didn't put something away that could be a mess or an accident.
Too often folks believe that dogs "outgrow" the usefulness of a crate. But when done with care, it can increase the stability of your dog, and make them more versatile from traveling, to boarding, to veterinary care. Even if you don't want to crate your dogs every time you leave, consider practicing a few times of month to keep the positive association fresh.
Even newly adopted adult dogs can be crate trained. The major thing to remember is that you have to be incremental with your crate training, and use food rewards liberally. Feed all of the meals in the crate for 3-4 months. Nothing inspires crate fondness like meals only being given there! Practice with you dog in the crate when they can see you, when they can't, and when you aren't home. A radio can help reduce stimulation and help your dog focus on a good nap. Exercise before crating practice can help associate the space with rest as well. Leave a treat as special crate-only option. Some of the favorites at our house are cow hooves, frozen pb kongs, bully sticks or pigs ears. I like to use a treat that take some time to finish, particularly one that involves chewing as it releases stress hormones. Some dogs prefer a cover, some prefer an open view. And be consistent.
When a dog feels safe, they are more reliable with commands and expected behaviors. They are less inclined to pace, to be destructive, to have accidents. The crate mindset is one that isn't automatic just because your dog has been crated- rather it's a willingness to respect the boundaries of space, and know when being asked to settle down from an emotional high for whatever reason. The benefits are vast, and it is one of the easiest things you can do to help have a happy dog home!