Only thing I don't get is why they have to be cages. Why not a nice wooden kennel or similar.

Perhaps down to manoeverability?

I'll start.

My personal view is that my dog's crates are their beds. They go to them freely, when they please, for peace, a rest, a chew, whatever, it is their place, no-one elses. Whe I go out, or at night, I crate them. Why, because I feel that when they are crated, I know they are safe and cannot get into mischief. God forbid anyone broke into my home, my dogs won't accidentaly be let out. It also helped with toilet training in the early days, and some training, using the crate for time out.

Now, as my dogs are passed those things, their crates are their own little pieces of space, that is private to them. (my bitch is in her crate as we speak, on her back, upside down, fast asleep )

Crates are a great idea if they are used in positive training and for the reason they were intended and not open to abuse.
Absolute fan of them. I use them for a new pup when I'm out or at night as I know they are safe. No room can be 100% safe as there's always something to chew on and get stuck in their throats. Training to the crate is done so that the dog see's it as a good place to go. I continue to leave my large crate up as my dogs love curling up in it. I have covered it with a blanket on most sides and my bitch in particular uses it especially when there are thunderstorms or fireworks, it's her safe place to be. Crate training has also come in useful as it was somewhere my bitch could be when she was spayed and needed to be out of the way of my then boisterous young male. It was her sanctury. Again it was useful when my male was injured and needed to be bed rested so to speak for 8 weeks. Now you try telling a BC to rest. As he was happy in his cage. It was set up in the lounge and then in the bedroom and he was happy as larry in it. Also I cage him at shows which I personally prefer to a benching chain as he's protected by any dogs that lunge out. He jumps straight in and often just drifts off to sleep whether i'm there or not. As both of them had been trained to a cage when very young and associate it with good things and a safe place to go. It comes in useful if things crop up or when I go away.
What I am dead against is cages used for just putting the dog in for ease of the owner and it infuriates me they are put in as punishment. They were never made for this.
I do think the problem sometimes with people against them is getting beyond the idea of a dog in a cage. Done correctly it benefits the dog in so many ways