Why is it common to keep skins during fermentation for red wine but not for white wine?

Keeping the skins during fermentation for red wine is essential because they contribute both color and tannins, which are fundamental components of red wine's character. The skins contain pigments called anthocyanins that give red wine its distinctive color, ranging from deep purples to bright reds, depending on the grape variety and fermentation process. Tannins, which are also found in the skins, come from the grape's seeds and stems, and they provide structure, complexity, and astringency to the wine. These characteristics are critical for the body and aging potential of red wines.

In contrast, white wines are typically made without the skins, which is why they do not exhibit the same color or tannin structure. The focus for white wines often revolves around the fruitiness and floral aromas, which can be expressed more cleanly without the astringency that skins would impart. Hence, the absence of skins during fermentation enables a lighter, crisper profile for white wines, which is preferred for their overall sensory experience.