While I graduated high school in '88, early enlistment in '86 moved me ahead of the curve slightly, so generally speaking I'm in the 'target group' the OP was referring to.
Really the 'answer' to the demographic, or more specifically why the systems in question have such a strong following is that unlike what came before them, these were the systems that put them in the hands of normal people. NORMAL PEOPLE didn't own Big Iron, and until the late '70's that's the only computers there really were. Even some of the early "hobbyist" machines (S-100, Elf) required a knowledge of electronics that greatly limited the people who could own one, program one, etc, etc...
Likewise the older systems, particularly mainframes had extremely low production runs -- thus increases value -- but always asking the question...
WHERE THE **** AM I GONNA PUT IT?!? -- much less pay for shipping.
Collecting mainframes is a rich man's sport; anyone can grab a '80's microcomputer off e-fence for less than $100 shipped.
Also, you have some stigma attached to 'big iron', particularly amongst the microcomputing crowd -- "Back room server geeks", "college ****'s who know **** about ****", etc, etc... Despite what todays FLOSS-tards run their mouths about, if it wasn't for Linux as a whole *nixisms were DEAD outside of the handful of universities and holdout businesses with their heads stuck up the 1970's backside. It also doesn't help that most of the 'big' systems prior to the late '70's aren't even as powerful as some game consoles; see how the Intellivision is basically a PDP-11.
That's the group that was left behind by the computer revolution of the '80's. NORMAL PEOPLE never had access to it... nor did they want to. Remember making fun of Unix for being needlessly cryptic and uselessly crippled? I sure do. DROSSDOS? How about this gem from the OS/9 manual:
UNIX: An operating system similar to OS-9, but with less functionality and special features designed to soak up excess memory, disk space and CPU time on large, expensive computers.
The REAL computer revolution in terms of normal people even having access to something you could sit down and use was driven by Atari, Commodore, Tandy, Sinclair, IBM, Microsoft, Borland, Lotus, Apple (to a lesser extent around here since I never new ANYONE who owned one and never even saw an Apple II in person until '88 -- admittedly I'm smack dab in the middle of Wayne Green country), even Coleco -- were the first 'computers for the masses', and that's why there's so much nostalgia for them and collectability to them.
At the same time the first generation of home systems still had a certain amount of "you have to be this smart to use them" -- by the time you get to where you could buy a Windows PC at Staples home computers were everywhere and even grandma could use them. That decreases the geek factor, the value, and anything that makes such platforms 'interesting'. You also have the problem said platforms just weren't unique -- while standardization did wonders for getting systems in people's hands, none of the unique platform specific quirks of the 80's systems even existed.
Without the nostalgia factor, uniqueness, and low (relatively speaking) production counts there's no collectability to anything later. It's like comics -- past the silver age they're not worth anything... and even silver age there are only a handful that are actually worth anything. The same can be said of computers -- a NeXT workstation or even a Sun Workstation is going to have more collector value than a Packard Bell P-150... They were DIFFERENT, as opposed to mass produced everybody's sister had one.
The room is closed to finished now. I direct you to the story of a recent haul for some pictures of it's current state:
