Obviously you aren't understanding the conversation that was taking place. Someone claimed the tablet would replace the Macbook Air, the guy you responded to told him why it wouldn't.
But to answer your question, a lot of nay-sayers (I am one) understand very well that because the tablet wouldn't answer our needs, it doesn't mean someone doesn't need it.
What we are saying, based on observation of the market, is that tablets in general, be them general purpose tablets or laptops with swivel screens, just aren't making inroads on the market. They are a small niche. The fact is, they have all the cons of both the PDA and the laptop, and don't have too many pros to outweight them and consumers are voting with their wallet on this one.
Tablets fit in between a laptop on a PDA. However, they aren't more portable than a laptop really. While they are smaller, they still require a bag of some sort you'll have to drag around, risk losing, getting stolen, or simply forgetting somewhere. They still require 2 hands to handle.
On the other side, they have mostly PDA like functionality (unless you count the WinXP tablets) like a rumored iPhone OS based tablet would have. Quick apps that can do quick things like listening to music, viewing a video or previewing a document, but not full content creation/editing capabilities and limited input like a full laptop offers.
And that's why they aren't catching on, the market isn't very big for laptop portability problems with PDA power.
E-readers on the other hand seem to be a good revenue maker. However, they have a low cost associated with their single use capabilities. If Apple does do a e-reader only tablet, on the cheap, this might be a good competitor to the Nook or Kindle and tied with the iTunes Book Store, this could be a worthwhile product. But a general purpose tablet like the Nokia N810 or the Samsung Q1 ? Not seeing it being more popular than the Apple TV was after the initial hype has died down.
