Makeahouseahome totally agree with you, if a dog is properly trained and secure why would they need to be put in a cage? And calling it a crate means nothing, you can call a prison a detention centre or a holding facility, it's still a prison.
We have dog beds in all the main rooms my dog chooses which one she fancies according to her mood - or sleeps with us - most of the time she chooses to be with whichever one's nearest us, sometimes she uses one in another room...Her sleeping habits demonstrate that she prefers to move around at night and sleep/nap in different spots depending on her mood, why restrict her?
As for returning to them voluntarily. People who've been in long-stay homes/institutions often don't want to leave them, it's called institutionalisation, doesn't mean that they are happier in enclosed institutions just that being restricted has become ingrained.
I think crates are particularly problematic if they are not big enough to allow standing, full stretches, and so on...older dogs with arthritis find it very hard to get comfortable and move around a lot in their sleep and in waking between naps...a crate would be extremely uncomfortable.
At some point no doubt the old red herring about dogs sleeping in dens will come up, a myth that's been a great marketing tool for the crate industry, but the people bringing it up will conveniently forget that: dogs have evolved so habits traced back over thousands of years will not be relevant; dogs in dens slept in packs so not cut off from other contact; dens were chosen not imposed and were most often large spaces like caves which dogs could enter and leave freely, not restrictive wire cages.
The only use that I can think of that's got a point to it that benefits the dog is when they have an injury and movement needs to be restricted, having said that when our dog had major surgery, we took turns to be/sleep with her downstairs so we could carry her out to pee etc...until she recovered and she recovered brilliantly.