I was using a PowerBook G4 DLSD (17 years old) just recently until it stopped taking in a charge (note it's not dead, just power delivery failed), at which point I got the closest recent equivalent, this 15" Surface Laptop 3. I had it loaded with Debian sid, and with a somewhat stripped back browser and LXDE, it handled most web tasks pretty much fine. YouTube worked, for instance. I shoved in 2GB RAM and an SSD, so swap wasn't that much of an issue. It loaded up various sites just fine like Amazon's KDP, Mechanical Turk, Reddit, all sites that also work in Mac OS X Tiger but TenFourFox isn't getting updates anymore. And
that was a recent upgrade from a 14" iBook G3 900MHz (20 years old). Which I only got because PD also failed on my Dell Inspiron 2200.
On desktop, until 2020 I was using an i5-2400 system, which I upgraded in 2021 to... a Power Mac G4 450MHz (23 years old), though I did switch out to a dual 800MHz Quicksilver (21 years old, 22 this August) on which I did all the same stuff on top of various Mac OS 9 gaming and music related activities, and even 3D modelling with ray tracing. If you want an easy, if unrepresentative group, you can head over to the
Early Intel Macs and
PowerPC Macs subforums of this very website and ask around.
Hell, even if you want to stay on macOS, Haswell Macs (~9 years old) are just new enough to have the AVX2 instructions needed for running Ventura without introducing more bugs than it ships with; Core 2 Duo can be used if you don't mind the occasional glitch due to those instructions causing errors that don't lead to halting and emulating.
If you want a few more representative groups who might use 10 year old computers... look to anyone that's not upper-middle class in a consumerist society. People in other countries, younger people/college students, people in lower class homes, people who act like they have $102,000 of debt (because, per capita,
they do), people who just don't like waste and want to use things if they still work rather than throwing them out when the new shiny happens. Maybe they have the means and just get fun out of getting something older to do stuff meant for more modern hardware. Curmudgeonly old people... George R.R. Martin still uses an IBM clone with WordStar to write the ASoI&F series, and if not already, that thing will be reaching 40 this decade. Industrial and even many scientific PCs are often from the 1990s since they still rely on software and ISA cards that you
can't replace. $2,500 isn't playing around money if you're just gonna recycle it after three years.
Even just ignoring all that, Apple sold the 2012 13" MBP for four whole years, meaning someone could get one in 2016 and use it until the model was twelve years old and still get official support.