Ezines is one of the article submitting sites that hasn't really suffered from the Google Panda update. The reason being their liking for unique and quality content which is exactly in compliance with Panda. That is why not everyone can get their article submitted to Ezine, because they accept good content only.
Really???? do you think they want a bunch of crappy articles.. its all about quality, every bad article they accept could ruin their reputation.
Ezine is one of topmost article directories, site admin knows very well that getting article publish will definitely increase ranking.I think they also consider whether site link in resource box is quality one or not. That's why it takes time to approve articles.
unknownpray and sarahk has answer that, ezine articles only accept quality content (those contents are not duplicate and it able to attract readership). This kind of articles require time to research. Imagine if you receive thousand of article per day, what would you do? are you take time to review it?