Wow.....How did it end up like this. You can always find examples of people doing things wrong, be it Breeders of pure bred dogs or owners of dogs who just let anything happen.
It is up to people to decide to desex or not. Desexing is done to keep things simple for joe blow average......Anyone can keep an entire dog or bitch with a little extra care and attention and never have any puppies. I have often got undesexed males and females and do not breed. But in Bitches there are several reasons for their health to get them desexed, so if they are not excellent for breeding I get hem desexed. Having lost one bitch at 7 from Ovarian cancer, which is percentage wise incredibly more common in bitches over seven.
However I keep my male dogs entire......testicular cancer is not a greater percentage and would definitely still happen if a dog had a vasectomy (maybe a higher risk). I have never had my dogs breed to bitches unless I wanted to breed. Lukey is a Stud dog Newfoundland. And in the past our Kelpies and GSD's
But I study dog behaviour and I train dogs and let me tell you that the average dog is greatly interested in bitches in heat. And if they can will chase one down. In the show ring on lead we can all control our dogs, but hey,.......Left in an open environment, any normal happy dog would just go for it. A dog has to be kept contained/on lead/or under instruction if a bitch is within sniffing distance. They are after all dogs And it is normal behaviour.
Most desexing is done, because most people do not have the safe environment ( good runs/fences) or the inclination to keep their dogs from getting into trouble. It is just easier to keep a desexed dog.......Less to worry about