Why are some wines fermented in concrete?

Hello there! I'm Dr. Vinifera, but you can call me Vinny. Ask me your toughest wine questions, from the fine points of etiquette to the science of winemaking. And don't worry, I'm no wine snob—you can also ask me those "dumb questions" you're too embarrased to ask your wine geek friends! I hope you find my answers educational, empowering and even amusing. And don't forget to check out my most asked questions and my full archives for all my Q&A classics.
Dear Dr. Vinny,
I read more and more about fermenting wines in concrete tanks. Concrete does not sound to me like a very human-friendly compound to immerse wine in. Would you please explain this process?
—Alois S., Idyllwild, Calif.
Dear Alois,
Concrete has been a part of winemaking for a long time, and it’s true that concrete fermentors have recently become fashionable again. There are some great features to concrete: They are neutral containers, with thick, temperature-stabilizing walls that are believed to soften a wine’s texture; concrete tanks are customizable in design and shape; and they're much more affordable than barrels. Most winemakers use them for fermentation, but others use concrete vats for aging wine as well.
I’ve been up close with these tanks and they are beautiful—don’t think of them like a concrete sidewalk—think of them like a sleek countertop or stylish sink. These are smooth to the touch, and it’s easy to see their appeal, not just functionally, but aesthetically.
—Dr. Vinny