The industry that provides antioxidant supplements to the world has tremendous inertia: enormous income and a very loud voice, and thus little incentive to react to advances in scientific knowledge that might reduce that revenue stream if acted upon. So despite the scientific consensus that ingested antioxidants are not in fact wonderful for your health, and may even be modestly harmful over the long term, the larger players in the industry continue onward as though it's still 1992 outside their offices.

On the other side of the fence, the public at large keeps buying the products as though it's still 1992, just as blithely ignoring what the scientific community has to say on the matter. Everyone wants that silver bullet to be available now rather than tomorrow, and wants it badly enough to buy lead painted up to a nice sheen if that's all there is. All in all it's a good reminder that any institutional knowledge or common wisdom is likely to be a decade or two out of date - it takes time for information to percolate, even in this age of instant electronic overcommunication. There is seemingly so much that everyone has to say, day in and day out, and yet the important data still takes years to get from point A to point B.

Here is a good open access paper on antioxidants and just how far removed from reality the common wisdom is these days. I imagine it will take a few more years of authoring similar review papers for the point to start to sink in:

Antioxidants are assumed to provide numerous benefits, including better health, a reduced rate of aging, and improved exercise performance. Specifically, antioxidants are commonly "prescribed" by the media, supplement industry, and "fitness experts" for individuals prior to training and performance, with assumed benefits of improved fatigue resistance and recovery. This has provoked expansion of the supplement industry which responded by creation of a plethora of products aimed at facilitating the needs of the active individual. However, what does the experimental evidence say about the efficacy of antioxidants on skeletal muscle function? Are antioxidants actually as beneficial as the general populous believes? Or, could they in fact lead to deleterious effects on skeletal muscle function and performance?

...

Experimental evidence does not support the "common knowledge" that antioxidant treatment greatly improves exercise performance and recovery. On the contrary, studies with antioxidant supplementations generally show no effect on muscle function during and after exercise.

Source:
http://www.longevitymeme.org/newsletter/latest_rss_feed.cfm