I understand why you're confused. Sometimes a heatpad can go years without malfunctioning (if ever) like mine did, and sometimes it'll malfunction right off the bat like my parents' did. Sometimes the temps may not be hot enough to burn, but might still be hot enough to throw off an animal's internal chemistry (I know it can wreck a frog's kidneys long before a burn happens). Someone who's never had a malfunction is a lot more likely to say you don't need one, but if you keep reptiles long enough you'll see it happen. Your BP could live up to 40 years, so the odds of it happening at least once during that time are quite high.
Edit: It doesn't always have to be a malfunction. Even just running normally can get too hot.