I always have a suspicion on a thread when people claim they just want to know something.
I like to play Mumsnet Bingo as soon as someone mentions people being defensive.
And more importantly, for reasons I can't articulate properly right now it disturbs me that someone who I'd vehemently opposed to cages sees them as necessary for what they referrer to as 'disturbed' dogs.
A number of people on this thread or either professionals in their field and amazing people who have devoted their lives and resources to all dogs without prejudice. They've simply answered why crates are used and for what. No one has said the op is not allowed to dislike them. Not once.
I wouldn't have bothered responding to this thread myself if I had realised it was not intended as a discussion, but as a vehicle for self indulgence.
Bunlion, I think your points are true. There are always ways to to address the points you have made without crating.
But I prefer a crate as in my case my dog needed to travel. It is far easier to have a crate when your dog regularly goes to a factory, travels on boats, goes camping at festivals and shows. Because I may miss something in dog proofing. My dog has always had the freedom she needs in all those places but we had the crate to keep her safe from others 
In regards to locking her in a dog proof room when visitors arrive. For me that is not an option. I'm trying to train her to socialise properly and learn boundaries and interaction.
In her pen she can safely watch and observe, rather than be lovked in another room, and I can work on her Settle command. This is done with clicker training too. The door is more open than shut during this process, it is open for longer as she learns to behave better around new folk.
The pen also out lines her space in a very clear boundary for my pre-schooler. It's as much for keeping small humans out as keeping a dog in 
I'm not being defensive as I don't need to be. But the above reasons are why I like to have a crate or similar, and find them useful for my dogs welfare.