Why is showing reviews relevant? Amazon doesn't take down reviews because they'd be prosecuted or sued for publishing the opinions of its members if they didn't

Why is showing reviews relevant? Amazon doesn't take down reviews because they'd be prosecuted or sued for publishing the opinions of its members if they didn't; they take them down as a product decision. It's not at all obvious to me that companies should be liable for the contents of reviews from their customers, even those that they have reason to believe are false.