Nostaglia, fun, brings them back to their youth, etc. Funny thing is that many of those components are likely way out of tolerance just sitting around. You can replace all the caps, resistors, and so forth with tighter tolerance, and better quality for pretty cheap.
One other thing. There are a ton of service bulletins available, especially for SB and HW series. So you can go ahead and build it, and then you have to modify it to implement the service bulletins.
I agree - it's mostly nostalgia from guys who could not afford them when young, as well as a trip down memory lane.
Newly minted hams don't seem to value these things very highly in my observations, preferring the newer gear.
But - like it or not, these nostalgia seekers are slowly moving on to greener pastures - so if you have them - sell them now.
Like most fads, these things have a use by date, and the day will come when you can't give them away.
I recently bought an old fully working IC2A (2m HT) for $2 at a flea market, with charger.
At the same flea market, I picked up some heathkit gear for $5.00 as well.
Most of this stuff came from silent key sales I would guess, but it shows that nothing is intrinsically valuable, except in the eye of the beholder.
Anyone who has trolled Ebay like I do, would have noticed the huge drop in interest in paying high prices for many "older" items.
From radios to sextants to japanese ww2 swords, the prices have dropped hugely in the last 5 years.
This will continue most certainly - it's called deflation.
It happened in the 1930's, and it is happening again now.
Like the popping of the antique furniture bubble, the vintage ham radio bubble has burst, or certainly will.
So if you want to sell it, do it now - otherwise you will get to know the monkey paw trap.
To catch a monkey, you put a banana in a secured cage with a hole just big enough for the monkey to put in his paw.
When a monkey sees the banana, and puts his paw in to grab it, he can be captured.
Because the monkey refuses to let go of the banana, so making it impossible for him to pull his paw out the hole.
Many people exhibit the same behavior in my experience, whether in keeping hold of dud stocks, or hoarding old stuff.
Let go of the banana!
73 - Rob