Dyno time is important to many of us Dom.
1. We want to find any issues on the dyno rather than on the track, hopefully find and fix before it costs a butt load of money. I generally budget for dyno time as part of a build.
2. Its an important "base tune" tool and, often, we can find power quickly that we might have left on the table otherwise or, for quite a while . Its nice not having to wonder if a converter is holding us back or, wind sheer etc.
3. We can know factually what timing range the engine likes, we can quickly and easily test different fuels , lash , header sizes etc.
4. We can spend some quality time looking at the carb as a data plot, seeing every little change in afr across the pull as well as air flow and fuel load, trying different spacers, carbs etc.
5. because we have a plotted tq curve and hp curve we can make converter/gear decisions a bit easier.
Its a tool and, imho, a very good one.
I enjoy dyno days- though they are exhausting - im always quite tired when we are done.

Then its all about car assembly and off to test and tune and, imho, "test n tune " goes better/faster because we have gotten some good pre-production work done, have data to reference and thus engine/carb/chassis tuning can be rather structured- at least, it works well for me and , knock on wood, i haven't missed my projected numbers by much or very often and, i'm still learning - hopefully!

My friends here , some who won championships in 2020 follow the same methodology and i'm fortunate enough to be asked to help with the tunes on those from time to time.
But basically: if your building for 800, 900 hp or up, its really nice to know if your built hit the numbers , if not, why and, if so- where you are before you start actually tuning the race car, boat, etc.

Its just another tool for me, nothing more, just helps us match expectations to outcomes as quickly and cleanly as possible.

I reckon everyone figures out what works best for them, gives them what they figure is their best chance for success.
We are soon to start on a little 500 hp Ford engine for a customer and it will go straight to the dyno to test, check for leaks, make sure we don't have any problems , can select the drivetrain values etc before installing everything in a new build - if we have any issues, i want to find them before the final build of the car.

Hope this helps.