Having played miniatures for many years, I believe part of the appeal is not simply the actual figures, despite how meticulously (and laboriously) one has painted them. The 3D effect of well-crafted terrain is also an important part of the attraction. You have to have a cool looking battlefield to go with all those historically accurate figures!
IMO, despite the excellent artwork of the Deluxe map boards, the flat, 2D, look was at least part of the reason the ASL in miniatures experiment never really took off. At least for me, having some nifty micro armor running around on a paper map just never lit my candle.
Today, I think part of the appeal of those mega-hexes is the space it allows one to spread out all the stuff and reduce the fiddle-factor of tall (and falling) stacks.
Besides, part of John Hill's original design was to intentionally give a miniatures 'feel' to the flat world of hex and counter games. Something I think he certainly succeeded at accomplishing.