Actually you can use them as external displays but requires some hackery. See https://ohmypizza.com/2023/04/converting-a-5k-imac-into-an-e...

But yeah agree entirely there. When upgrading from my somewhat cranky old 5k iMac a while back, I decided I'd never buy another iMac. The 24" was out. So I bought a Studio Display and a mac mini. At least I can upgrade the computer separately, which has happened already (M2 mini -> M4 mini). I expect the Studio Display to last a long time as you can actually buy parts for it.

Yeah, the single reason i consider that buying an imac makes no sense. We have a bunch of older imacs lying around at work, it is such a waste not being able to use them as external monitors.

At some point Apple add Airplay display sharing on Macs, so you can do that.

I'll be doing that with our 5k Intel iMac. Of course the Mac has to be running, which is more power draw than a monitor alone.

Very strange indeed. So much for sustainability and environmental friendly.

You can use an app like Duet or other apps like these.