Although renter's insurance is usually not required by law like car or homeowner’s insurance, you need it for the same reasons. Let’s say there is a leaky roof. The landlord is likely responsible for the roof repair but what about your TV or stereo equipment that got wet and broken? Renter's insurance takes care of your personal things in situations like this.
Renter’s Insurance will also provide you help with temporary housing if god forbid your apartment burns down. Renter’s insurance can also help with liability issues like if you forgot to shovel your front steps, someone slipped and now wants to sue you for medical expenses. These are hypothetical instances that renter’s insurance would save the day.