Ok whopping post coming up, but I have been musing on this point overnight and have come back and read the posts after I posted last night and would like to contribute again if I may?
Two of HoneyDragon's points hit the right note for me:
"Its not a case that dogs shouldn't have crates. It's that some PEOPLE shouldn't have dogs."
and
"And as long as dogs generate profit, company's will spin any old shit to get cash out of new owners, hence what used to be referred to training aids are now marketed as magic solutions to stop barking, pulling, chewing etc."
In my early days of having dogs (late 80s, early 90s) crates were around, but only available from specialist suppliers, the ones that supplied to breeders etc, usually by mail order, so most pet dog owners weren't aware of them and if they were, were less likely to be able to get hold of one, unless they were the type of owner who was doing tonnes of research and giving lots of consideration to taking on a pup/dog and how they were going to take care of and train it etc.
I was very keen to learn as much as I could and do things right for my dog, so was registered on some of the early online dog forums, which in the main, back then were mostly dominated by Amercian posters. I left after getting into a fight with an American breeder, who bred small breeds and was apparently regarded as top of her breed. The fight was because she was not only keeping her dogs in stacked cages for the lion's share of the day, she was also advocating and in fact instructing new pup owners (of any breed) that it was fine to get a pup, cage it and then go to work all day every day. In one spectacularly memorable fight, I was rounded on and attacked by large numbers of posters because I had the audacity to suggest to an owner that it wasn't ok for him to crate his young dog for 8 hours a day while he went to work and then never let if off the lead during the only walk it got every evening. Apparently I was clearly bonkers, knew nothing about dogs and was suggesting he should endanger his dog by leaving it loose in the house (I wasn't actually, I said that I had no clue why he had a dog, as he crated it for 8 hours a day, then gave it a short lead walk and frequently crated it again while he went out for the evening.
) and that I was stupid if I thought dogs should be allowed off the lead for exercise, as they could get lost or hit by a car.
No matter what I said, I was repeatedly and nastily attacked (no moderation on that forum) and it was clear that my words had hit a nerve with a large number of dog owners. There were, iirc, only two people who attempted to agree with me and they were soon shot down in flames. 
By the mid 90s, crates were available on the internet, again from specialist shops and you probably wouldn't know about them, unless you were heavily involved in dogs in some way, iyswim.
In 1998, when we got our first (and only) pedigree/non-rescue dog, they were becoming more common and I think some of the larger pet superstores that were springing up had started to stock them. (I know we saw some when we were buying everything we needed for our pup, but we didn't even consider them at the time, having never had or needed one with any of our previous dogs.) The problem with that was that they didn't come with any advice or instructions on how to use them and as they were readily available, anyone could buy one - although they were £££s.
Since then, their availability and use has increased dramatically - they are sold, as HoneyDragon's quote above explains, not as dog beds or training aids, but as solutions, to stop chewing, soiling, 'anti-social behaviour' etc and people tend not to think about it any further than that.
When I was younger I used to keep pet rats. They had huge great big cages with lots of things to do, they were healthy and seemed happy. I thought I was doing right by them and as long as I did everything the books recommended for their care all was well. These days, I wouldn't contemplate keeping a caged animal of any sort. I now don't think we have the right to restrict any animal's freedom to that extent. I have grown up, thought about, contemplated and researched things and I no longer think the way I used to about animals.
As with other matters of ethics etc, I am still not quite there and probably never will be, as I hope to continue to grow and develop for the whole of my life. As a result, not everything I believe to be right/wrong is all sewn up in a nice neat logical package. So I don't keep small furries, but I do keep dogs and I sometimes find myself wriggling uncomfortably, when I hear/use the words 'dog owner' because, although technically true, I am not quite at peace with the idea of 'owning' another living creature - it doesn't sit well, yet I really can't bear the thought of not having a dog in my life. For me, my dogs are part of the family - but if I'm honest and stop fooling myself for a minute - I own them ... and don't get me started on how confused I am with regard to my right to 'train' and 'modify' behaviours to suit myself/society, rather than the needs of the dog. I clearly still have a great deal work to do on this, but in the meantime, I can't contemplate my having a life without dogs in it, so all I can do is my best.
My point is, we could extend the argument against crating onwards and upwards until we reach the point where we question keeping dogs at all. Pet ownership is controversial, some would argue that no animal, humans included, has the right to own and dominate another (by controlling their freedoms etc).
I know I've waffled on a bit there, but what I am trying to say is that we are all treading our own paths, all at different levels of learning and understanding etc and I'm pretty sure most of the dog people on here adore their dogs and only want the best for them. What they do comes from a place of love and they probably wouldn't be posting on here for advice if they didn't truly love their dogs.
Debate is good. I think it's important to have these discussions to help people - like me - to think more deeply about their choices in relation to keeping, caring for and training dogs. We need people to question what we do, to help us think about things we might not have considered and confront things we generally prefer to push to the back of our minds.
Yes, there are people who use training aids/tools without considering the whys/hows/wherefores and there are others who will never care enough about the animals in their life to even consider treating them with the care and respect they deserve - and the commercial dog training market feeds off those people. Their interest is not in the dogs, but in their profits and unfortunately, that is never going to change. 