Most ski helmets don't have a brim or visor, and that's perfectly fine for the majority of skiers. A clean, brimless design is the most common style you'll see on the mountain — it's lighter, has a sleeker profile, and won't interfere with any goggle shape or fit.
Without a brim, you won't get built-in sun shading or extra deflection from rain and snow hitting your goggles. If you frequently ski on bright, bluebird days or in wet snow, you might miss that coverage. But for freestyle riders, racers, or anyone who prefers a minimalist setup, a brimless helmet is usually the way to go.
The bottom line: unless you know you want a brim for sun and weather protection, going without one is a solid choice. Just rely on good goggles and sunscreen for bright conditions.