It basically only exists for the sake of testing without buying a Mac. Since it pulls in an entire Cocoa/Carbon/whatever stack, it uses an intense amount of ram and performs slowly.
I'm not on Windows, so I haven't used it myself, but you're the first person I've heard complain about it since 4.0 dropped (though, granted, I don't listen very hard).
More important, I would think, is that it supports the web standards that Google has a vested interest in seeing flourish, and it would be another shiny logo that might get clicked rather than the IE7/8 link they put up out of necessity.
It's not targeted at real people who have to make a choice about which to download. It's been pretty well established that the only people still on IE6 are stuck behind IT policies that don't allow for upgrades. It's just a political statement, then, an attempt to drive home the point that IE6 is an ancient and decrepit bane on society and technology. The more sheer embarrassment that you can pile on top of these IT departments, the more frustration you ladle into the end users that they can direct into getting their company policies changed (rather than, hopefully, directed at you), the better. I think showing a wider variety of actually viable browsers makes that point better (hell, throw Opera in), because it makes it obvious just how far behind the rest of the world has left IE6.
