The imac is unusual in that it doesn't offer everything offered by the classic desktop, and it's still not that cheap. Even in terms of ergonomics, I like being able to adjust height. The imac cannot do this out of the box. It requires purchasing an arm, and the one carried by the Apple store is reviewed somewhat poorly on their site.It burns down to two things: consumer interest and accessory makers.
It doesn't take a genius to figure out that desktop users is a dwindling percentage of computer users. Only those who need serious power buy a tower these days. Barring that, a laptop or even iPad is suffice for most people.
I hope this is NOT true, if it is OR the new IMac is crippled, I have the parts to build a great PC in the New Egg Basket just waiting to push the button BUTAll the evidence says the Imac will come in March and not sooner.