Take off the dark glasses.
Who wants the iMac G5. Well, for startes, someone who wants more than a MacMini can offer but doesn'tneed the full flexability of a PowerMac.
Someone who has a very limited area to keep a computer in. Someone who doesn't want the clutter of having the computer seperate from the display and the extra cable(s) that would be in use, including a second power outlet. (Although I strongly recommend that computers be kept an good surge supressors.)
The iMac G5 takes up less desk space than a MacMini plus screen. Come to think of it, the iMacG4 is pretty effecient on desk space as well.
Remember everyone has different needs and esthetics.