I'm also an Apple shareholder and I disagree with you. First off, the AIO iMac and Mac minis also represent a niche markets. Look around, what % of the market are AIO computers? Very small indeed. The most common desktop computers sold in the US and Worldwide are towers of some form.
You may be right that Apple's line-up is a thing of beauty but it does have a gapping hole in the desktop line-up. These threads occur in virtually every Mac centric bulletin board, why do you think that is?
Saying these posts show "a lack of sophistication when it comes to marketing" is pure arrogance on your part. No one has convinced me, nor the inumberable other posters pointing out this hole in the desktop line-up, that Apple couldn't sell more computers and be just as profitable as they are now.
Let's assume Apple develops a tower aimed at the market you're describing. The costs wouldn't be too high for development because the tower that's used for the Mac Pro could be used in a slightly altered form. Now, it would come down to guaging the market.
Apple already sells more notebooks than it does desktops; I believe the ratio has come to nearly 2:1 now. So, we already know that the desktop market is gradually shrinking. Mind you, it will probably level off at some point, but it will probably level off at something around 20% of any company's total sales. Knowing this, why would Apple commit the resources to develop a product whose market is gradually being eaten away? This is one nail in the coffin for your tower.
Now, let's assume that Apple would be able to develop the tower and make enough sales off of it in order to pay off sunk costs like design, marketing, production of the first ten thousand units, etc. Would the product continue to sell in numbers great enough to give Apple it's 25%+ profit margin? Since the iMac starts at $1200, and the Mini ends at $800, Apple would have to somehow convince buyers to forgo the built-in display, and cough up more money for a what is essentially a better Mini. Since $1000 seems to be a good in between marker, let's say that's the entry price for one of these towers. How many consumers do you think, aside from yourself, would go into a store, look at a $1000 machine with no moniter, and then at a $1200 machine with everything built-in, and say, "I want the $1000 machine."? There's a major conflict in terms of price points and features. Granted, the $1000 tower would be more powerful than the iMac, but how many average consumers are going to think about this? For the average computer know-nothing, it's easier to buy everything in a single package. This tower only appeals to those who are going to game, or who need a powerful desktop.
Well, I have good news for you. You can get the powerful desktop, it's called a Mac Pro
Not in desktop sales.
Quarterly Report_______Desktops in 1000s
12/25/04__________________623
3/26/05___________________608
6/25/05___________________687
12/31/05__________________667
4/1/06____________________614
7/1/06____________________529
12/30/06__________________637
3/31/07___________________626
7/25/07___________________634
Apple sold more computers in the 4th fiscal quarter of 2005 and the following 1st fiscal quarter than they have in 2007.
No PC maker is doing well in desktop sales, esspecially to home users. By far, most desktops that are sold are sold to the business market.
PS: merge your posts next time by double-quoting.