Think of all the things you own in your apartment. That fire, tornado, or even a thief could take away or destroy some or all of your valuables. Can you afford to replace those items?
What if a guest slips and falls in your apartment due to your negligence? Do you have coverage for that? If your answer is, "My landlord covers that; it's part of my rent", that's not necessarily true. Your landlord's insurance only covers liability for which he or she is responsible. It doesn't extend to your liability. Fortunately, your renter's policy provides liability coverage. So if someone is injured in your apartment due to your negligence and that person submits a claim or files a lawsuit against your, your renter's policy will help protect you.