Why, you ask, would a person need a wick trimmer? For starters, you should be trimming your candle wicks before you re-light them anyway! It keeps the flame reasonably sized and steady, which greatly reduces your risk of catching something on fire that you didn't want to catch fire.
So why the wick trimmer specifically? Because the angled snippers trim the wick, then hold the spent wick as you lift it out of the candle. They work great! Plus it's just gratifying to have such a specific tool in your arsenal.