Of course you don't need a Little Stopper. But they are fun, if expensive, and open up a whole world of landscape photography opportunities denied to you if the weather is too bright, or quite frankly just too dull.
You're standing at the perfect viewpoint. The early morning mist is rising gently, there's a smell of Spring in the air. It's predawn, but you know what exposure you're going to need, and how long you'll be waiting for the first rays of sunlight. 20 minutes later you've got the shot, and are on your way home for coffee.
How often does that actually happen?