I used to work in veterinary medicine, and there are plenty of vaccine conspiracies in the pet owning community. They cause everything from seizures, to allergies, to autoimmune diseases, and more, according to some of these people. Breeders are a huge contributor to this, which leads to plenty of arguments with vets and pets running around unvaccinated.

It's expensive to get litters of puppies vaccinated, and whackadoodle (I used "doodle" for a reason) theories are a great cover for why you are sending home a puppy with zero medical history outside of hand written worming dates. Unfortunately, it's harder to educate people when it's way cheaper to believe bullshit.