Parasites can be common. Fleas for example are very common and annoying. How I treat and prevent parasites takes great care as I am dealing with chemicals and medications that can have an impact on the health of my dogs and puppies.
Fleas & ticks: I start out very conservatively. I do not use chemicals in my yard. My dogs walk on grass, eat the grass, roll around in grass and that means that even chemicals deemed safe may not if consumed or licked off paws. I start out with natural repellant sprays like Cedercide or Wondercide, (I am not paid for my recommendation) if that stops working, I am in south Central Texas after all, then I move on to topicals in addition to natural repellants. I have one dog I use a collar for (and I do understand the risks but he had flea allergies and it takes a bit more to protect him). I do not use any harsh chemicals on my litters/puppies. The side effects of oral treatments like Bravecto are absolutely frightening and I will not take that risk on an 8 week old puppy. My job is to keep them healthy and safe until they go home with you. If the issue is bad, I may use Capstar in addition to a bath before they go home. So that might mean you may find a flea or 2 while you consult with your vet and do your own research on which treatment is best for you. This is how I have chosen to control external parasites I understand you may choose a different way and you are free to make that choice.
Worms: I do use common de wormers and parasite prevention to protect our puppies from internal parasites including coccidia. Internal parasites are common which is why we have a strict deworming schedule. But with that being said a positive fecal does not mean your breeder is fifthly or dirty. These parasites are common in the ground, in water, in feces, all places puppies play in or are exposed to. I do a fecal at their 8 week check up and if by some chance it is positive after all the treatment we do the vet will treat your puppy before going home.