That's such a BS attitude. Why doesn't Apple just roll their previous models down into lower price slots? Or what, do those older models just become junk the minute the new models are released? There are a lot of people out there who buy PCs just to do a little email and Web surfing and they're not looking to spend over $1000, not even close. Why wouldn't Apple want to offer something to that buyer? Not everyone needs the latest and greatest. The iMacs that were out last year should have been pushed down into the sub $1000 range. Same for the MacBooks. I don't know what that would hurt and there's no way to make the argument that those machines would be "junk."
Apple stays ahead of the game by rolling out new tech that makes previous models "obsolete". They are THE king of this practice.
Only now is it becoming more and more difficult for them to do this as the models that get replaced are certainly not "obsolete" or "junk" by any standard. How could they be? They were "state-of-the-art" 6 MONTHS AGO! Keeping the old white macbook and the 17" mbp IS an example of what you're asking for, and its a new move for Apple. For the last few years through the move to Intel, the older models went to the refurbished category and were sold that way under the same concept, (buy slightly older for slightly less).
This has always been popular with those in the know for consumer buying.
But today, with rapid onset of faster and more powerful computing technology, its becoming more and more difficult to convince someone to buy the "latest and greatest," as it is only slightly "greater" than the model it replaces (which is dangerous when the product undergoes a major change away from a well adapted and accepted form.
ie: White Plastic Macbook = powerful and familiar
Standard shape aluminum MacBookPro = Very familiar, very powerful
New MacBooks = sexy, unfamiliar, more powerful?
New MBPs = sexy, unfamiliar, more powerful?
By keeping the 2 older products in the line, they will manage to not scare off the old folks who have waited until now to pick up the $1100 mac laptop they've been saving for. Its the same one that 2 of their children use and the same one they bought for their grandchild who just started college. And, oh my, its now only $999 with greater looking spec numbers than they remember seeing.
They also won't scare off the photographer who is just now finishing out the 2008 wedding season and has been counting the days til he/she can pick up a new MacBookPro to edit through the winter on. If that person, who has been too busy to keep up, shows up at the Apple store and doesn't see a laptop that looks like the powerbook or 1st gen mbp they have in their bag, they might turn right around and walk out.