True - the question is what are people actually waiting for? We've seen some big advances on laptop/tablet-sized screens (from Apple and others) but the world of 5k3k and 6k panels doesn't seem to be offering anything substantially better than the Studio Display or the Pro XDR.
The Studio Display is substantially the same 5k panel - just a tad brighter - as a 2017 iMac - and I don't see anything dramatically better at 5k3k resolution with - say - a (burn-proof) OLED panel, local dimming or high-frame-rate on the market.
There are now a couple of interesting 6k/32" options much cheaper than the Pro XDR - but AFAIK nothing with any sort of local dimming, even the limited number of zones on the XDR.
Last I looked, Apple don't make display panels - obviously they've found some way of sourcing new tech "custom" panels for the iPad and MacBooks, but do they sell enough desktop displays to commission a novel panel? Esp. since they'll probably only work on Macs with TB5 interfaces.
The issue is that the currently users have two options from Apple. Once is a 6k they cannot afford and aimed at niche pros so they are then left with a 27" which really at its core is a 2014 iMac monitor. Yes it has gotten P3 and brightness improvements in the past decade but its still at its core a 60hz 218 ppi 27" 5k screen that can't display HDR so users are naturally going to see their Macbooks which is Mini-LED 120hz and think that would justify the price and hold them over for many years wheras spending a lot of money on something that is at its core a monitor tech nearing 11 years at this point seems to be an issue for most.
The monitor industry is mostly geared towards PC/Gaming so 4k high response time has been the focus which is the complete opposite of Apple as they are in their own world with high PPI displays which is why there has been no advancements outside of Apple. We are now just seeing the competition come out with lower quality versions of what Apple has been doing at bargain prices which is a very good option for people.
As you noted Apple doesnt sell many desktop displays and this monitors is something they are not focused on as Apple isn't in the traditional display business. Their displays are more Mac specific accessories.