It's because the homepage is cluttered with features that new visitors don't want. All you should have on the hompage is a header graphic, navigation and a perhaps a login form. The rest of the page should be full of large, legible pictures advertising your MMORPG or other service. Here are some successful sites that use what I am talking about:
You do not need all those fancy features like what time it is, "welcome guest", last seen threads and suchlike "luxuries" on the homepage. To be honest they are useless. If I really wanted to know the time I'd look at my PC clock! If you must, you could squeeze those statistics at the bottom of the page.
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