Well, I'm a vet and got my first dog cage in 1995, after my pup chewed through the telephone wires and nearly gave himself a nasty obstruction. Before then I was worried it was "cruel" but he took to it like a duck to water and became far less anxious as a result. Later on we got rid of the cages, and he wasn't impressed!
I have seen dogs injured and ill in numerous ways that would have been prevented by using the cage, especially overnight. Of course owners watch their puppies pretty much all the time, just like parents do toddlers, but for that 5 minutes when you answer the door/ nip to the loo they are as invaluable as the playpen was for my toddlers. Can't understand why you can't see the similarilities in that comparison, tbh. Awake toddler requires constant supervision or playpen if supervision not possible. Awake puppy the same. Sleeping toddler in cot = sleeping puppy in crate.
My aunt had a real problem with her dog with fireworks. He was so distressed trying to get into small spaces (eg under the tv/ sofa) that he was at real risk of hurting himself, and she tried everything. I suggested dusting off his puppy crate, and he settled immediately, after months of sedatives/ behaviour therapy/ you name it. Just reinforced to me that dogs in distress seek a safe sanctuary- their cage. Any time my own dogs were upset or unwell they headed straight for the cage.
Yes they can be abused, but most people who go to the bother and expense of buying a crate have researched and are responsible. People do far worse things to dogs, believe me
A lot of chewing puppies seem to end up on the street or on effin Gumtree, where they get through 3 or more feckless owners in their first year. IMO, the clients who come in with a new puppy who have a crate and have researched it are also the ones who have researched having a pup, and are far more likely to be responsible owners than the eejits who bought a pup because it was cute, but come in complaining to me that it "pees everywhere!" at 10 wks old
and chews all their stuff. Most people who crate their dogs while they pop out are acutely aware that their dog is in the crate and only leave it for short periods. Others seem to think because it's "got the run of the house" it will be happy on its own for 8 hours a day. It's really not as black and white as you would like to paint it.