This is a common reply from new dog owners when the subject of crating is mentioned.
Dogs have a natural "den" instinct that dates back to their ancestors.
Crates give dogs security and their own special place.
My female loves her crate and feels most comfortable there.
Dogs are protective of their crates. If I go in and re-arrange his blankets, my male immediately goes in to inspect and re-arrange his "room".
Security for you. When I go to work I have peace of mind knowing my dobes are safe and free from harm. They cannot destroy anything or get into something that might harm them.
Crates bring your dog closer to you. The crate is placed in your home (usually in the kitchen or living room), and is not isolated away from you in the basement or garage.
It gives your dobe tranquility. If your dog is tired or not feeling well, a crate is perfect. It allows them to rest and be comfortable without interuptions.
Dog training is easier. It has been proven that crating makes housebreaking and other training, easier for you and the dog.
Traveling is much more enjoyable. When you travel with your pet it is safer for him and you (no jumping around while you are trying to drive). A crate is a godsend on vacations when the excitement of new surroundings take its toll on your dog. Dogs can quiet down and rest easy when they are welcomed by their own familiar place.
Now you know why crates are popular and beneficial, to your dogs life.