Where did you get the figures? 25% seems abnormally high to me, seeing as I'm in the pet industry (for the past 20 years)and I've seen thousands of dogs, with only a small handful of them having Pyrometria.

If the dog gets it, it needs immediate vet care. Spayed dogs cannot get pyrometria. Spayed dogs do not produce unwanted litters.

But that doesn't mean that every dog that's not spayed is somehow going to get pyrometria, mammary tumors or produce unwanted litters. Mammary tumors are often benign and dogs live for years with them with no ill effects(from my own experiances with dogs in my work). Dogs that are intact can be kept their entire lives without ever having them produce a litter of puppies or ever having a health issue.

Spaying and neutering can give health benefits, but it's not something I think EVERY animal should have done. I also don't think someone is a bad owner merely because they don't have it done.