Why would you need different models like "accessory recommender"? If they have enough data to conclude that purchasers of itemA are highly likely to purchase it

Why would you need different models like "accessory recommender"? If they have enough data to conclude that purchasers of itemA are highly likely to purchase itemB, why not just recommend itemB, even if itemA and itemB are both vacuums and a few people will complain about that on technology forums?