Being able to "falsify" the hypothesis that hedgehogs collect apples on their spines is actually non-trivial. It's not like it's simply a matter of observation, if you see a hedgehog and it doesn't have any apples stuck to it, maybe it just wasn't hungry or didn't have any apples nearby. You read it in a book and your books are expensive and rare and contain much that is useful to you every day. You don't have time to just watch hedgehogs all day, you're one of the few literate people in the middle ages; there's beer to brew and gardens to tend and homoerotic poetry to copy in secret. So just because you're one of the few people who knows what nullius in verba even means doesn't mean you can apply it to your life, it's not practical and sometimes you gotta listen to Pliny even if he did lose a fight with a volcano. If everyone tried to see if wolfsbane was poisonous instead of taking his word for it, there wouldn't be anyone left to feed the hedgehogs.