they may be pregapped from the factory, but it doesn’t gaurantee them not being damaged/bent during shipping. Sometimes they don’t have the cardboard sleeves to protect it.
so yeh, you always need to double check the gap. Don’t forget to anti-sieze the threads too. you wouldn’t want the plugs to get siezed in the block. this usually happens to high mileage cars though that never get a tune-up.