There are a ton of older iMacs on the used market, and if you have one, it's a fair complaint that you can no longer re-purpose it for whatever else you like. Ideally if I got a mac mini I'd just hook it up to the screen I already have, rather than spending another $2k on the only other option the brand sells.

Additionally, not having that option lets the manufacturer have control over how much value a product retains after it's useful life. Apple already does this in a number of different ways, and it's disgraceful. iPad too old to get new updates? Recycle, it's not like your backup included the versions that did work for your OS version, can't do much with the hardware. Battery dead? Recycle! Already have a 5k iMac but want Mac Studio for more performance? Well you better like spending a whole lot more for exactly no new value.