An old car can still drive on current roads. There's may be no aircon, only AM radio and no airbags, but there's still horsepower and size to do what cars do.
Then, cars rust and naturally become rare and expensive to restore to a running state, and almost all of the appeal is that you can show off in them, displaying how much money you can afford to spend on a hobby.
Old computers are pretty cheap and are limited to old software, and there's nearly no showing off other than on HN.
Surprisingly, a lot of the Internet is still accessible to these old dinosaurs, through the efforts of retro enthusiasts. A search engine like FrogFind reformats results for the earliest browsers like Netscape Navigator, and kind of "text modes" the pages. There's even virtual plugfests like GlobalTalk that links together retro enthusiasts' printers over the Internet.
Some of us had found many uses for our computers while they were offline, so I don't really get why you're implying they are useless without using the internet.
And I'm saying that as someone who only had access to a computer for about 4 years before we got internet access.
Many countries in Europe are now restricting access to cities to exclude even what would be considered relatively new vehicles. For example, Amsterdam's plan includes a transition to a zero-emission city center by 2030, and is already at Euro 4 emissions, affecting many vehicles from the 2000s. Germany's cities are also well ahead on emissions restrictions, as is Paris. No classic for you! I think only one of my cars would be allowed to operate in much of the Randstad today, but thankfully I don't live or work there anymore.
Meanwhile PDP-8 systems like mine are selling for in excess of €6k these days, and someone recently paid €1750 for a NeXTstation Turbo Color like mine, to say nothing of the other 20+ 60s, 70s, and 80s systems in my collection. I regularly remind my wife: if I drop dead unexpectedly, SELL that stuff, don't junk it or give it away.
A random 1950s-1970s car in serviceable driving condition can be had for a few grand around here, but Millennials having kids, nostalgia, and money all at the same time, not to mention COVID madness, has shot old computer prices through the roof. I expect that market will crater when they put us in the ground, much as the vintage car market is coming down a bit as we lose Boomers without gaining as many younger people interested in old cars. Populations moving to cities means that parking your vanity car (if classics are even allowed) in addition to your commuter would represent a significant uplift in ongoing expense, which will probably help to keep that market depressed.
Just because you can't find a useful purpose for an old computer doesn't mean they don't have any. For example, any computer, regardless of age, can be used to write a novel.
Then, cars rust and naturally become rare and expensive to restore to a running state, and almost all of the appeal is that you can show off in them, displaying how much money you can afford to spend on a hobby.
Old computers are pretty cheap and are limited to old software, and there's nearly no showing off other than on HN.
Whatever rocks your boat I guess.