for anything... there is no excuse for Apple to implement at least 120hz for a monitor that cost $1600 dollars.
Actually, there is. It's just that you think "there's way cheaper displays with higher refresh rate" and refuse to understand the context. To me, it sounds like "that Ferrari costs $400K and only has two seats!"
Higher resolution is mostly useful for gaming, but this is not a display for gaming.
It is useless for videos, almost useless for photo editing and most other uses this display is meant for.
So, it'd just be a nice-to-have for a smoother interface, which is very good for phones, where you're constantly scrolling and directly interacting with your fingers in front of the screen, which have "infinite framerate".
Also phone apps are constantly switching with animations and that's better to see on high refresh rate. Not quite the case on Macs.
What you see on a computer is mostly still images or things swapping with no animations.
High refresh rate at 5K is not a joke to handle for whatever computer is connected and I'm not sure how well adaptive refresh rate can be handled on an external display.
Higher refresh rate also influences other things such as thermal and power consumption and room for components you need to handle it.
I mean, it sounds like a lot of work for a nice-to-have that's mostly to see your cursor move more smoothly and I think they mostly feared inconistent results on some older models and almost useless stress on the device.
60hz has been a standard for professional displays forever and users don't seem to be obsessed with refresh rate.
Apple has always been conservative with this things, they choose a balanced experience for you instead of giving you some option that's probably not going to be what you should pick.
Sounds very reasonable that they focused on other things that matter much more for those who buy this. In general, it's not at all a must-have feature for people who want this kind of display, so it makes sense even just to save that money (these are devices for a very niche market, that's why they cost a lot).