During 2008 James Reasoner wrote more than a million words for publication (http://jamesreasoner.blogspot.com/2008/12/wrap-up.html). That's about 2,800 words a day, every day, for 365 days. In his case the result was 13 novels.
If I produced that many words for publication during any given year I would generate--give or take a few--365 short stories.
Imagine writing a short story a day, every day, for 365 days.
Now imagine finding markets for them. Real markets. Paying markets.
The markets are there. I already write for some of them. I've often had two stories in the same issue of a magazine, and have occasionally had three stories in the same issue, but to place 365 short stories in a year would mean filling some publications cover-to-cover several months in a row.
Now that's a challenge.