I use one - yes it is a cage, I don't mind it being called that at all though.
With toilet training, it encourages them not to go because they don't want to go to the toilet in their bed and can't get anywhere else...that's not why I still use it, he's housetrained.
It's safe, he can't chew wires or coins or batteries (all things he likes to chew), he can't fall off things he's tried to climb up and he can't lick the cats to death, lol.
He chooses to sleep there with the door open, he takes his bones in there to eat them in peace - he's fine when he's had to stay at the vets because he's used to it and it was a godsend when he had to have an operation and he needed weeks of crate rest afterwards.
The door is never shut over if there's someone about, it's only ever shut if he's left so he doesn't kill himself with no-one there to tell him to drop and leave whatever it is he's got his eye on.
The plan was that when he was older I was going to get rid of it, it was purely to keep him safe while he was little...unfortunately he still thinks he's little and has never grown out of chewing, despite having someone with him nearly all the time telling him what he can't chew and plenty of opportunity to chew his own things - the little sod just likes chewing, lol.