Quite simply because people want a cheap macintosh computer that they can use for gaming.
Which is a quite different issue from the current state of the mini or the market Apple has built it for.
I think people look at the mini as a console because of all the features Apple is touting (HD movie playback, the iLife suite, DVD burning etc), if you could play games well on them, I bet they'd be much more popular.
No actually PC gaming over the years is becoming less and less popular, while console and handheld gaming have become more popular.
Since the mid 90's sales of PC gaming have steadily declined to the point they are about half of what they were at their highest point.
In 1998 PC gaming software was at $1.8 billion dollars in revenue. In 2005 PC gaming software is at $953 million dollars in revenue.
In 1998 console and handheld gaming software was at $3.7 billion dollars in revenue. In 2005 console and handheld gaming software are a bit over $6 billion dollars in revenue.
but this isn't acceptable for todays's pc standards other than coporate use....
So far benchmarking of the Intel mini shows its fair with 2D gaming and suffers at 3D gaming. What barometer has gauged that 3D gaming is an absolute must for any modern computer?
If that were true Dell would not be able to sell its XPS 600 Extreme Gaming box for $4200.