It's the format.
An old post from Wet Asphalt with a lot of good thoughts about why so many literary magazines are bad and how we might make them better.
My point here certainly isn't that literary magazines should stop publishing unknowns. Rather, literary magazines need to require a lower entry cost in time and money to make it easier for readers to take a chance on them. Because that's what we're doing when we buy a magazine of short stories and poetry by writers we've never heard of: taking a chance. The editors of literary magazines need to start recognizing that, stop blaming the readers, and realize whose fault it is that their magazines aren't worth the risk.