Since you are a NMRA Life Member, and I have been model railroading on and off since 1959.....
Could it be ....
Cause the NMRA has not specifically set up manufacturing/supply criteria to the Producers/Manufacturers/Suppliers of our Hobby?
I have several theories on why this has never happened...however; I am speaking directly to a Open Letter from the venerable John Allen, who wondered why the NMRA does not seek out Prototype Standards.
Yeah...and I hadn't even started N Scale yet.
Duh Me? and here is where I am about to give the NMRA some slack....
I did not fully understand what John Allen was speaking till at least 2015 myself, when I ventured to run a Brass ATSF 2-10-4 myself over 19 Inch Track.
After viewing this video and other published thoughts and criteria, I got lazy myself and simply went to Commercially (readily) available 28" Radius Kato Unitrack. Yes, I Forrest Gumped my way into using broader curves.
Okay...28" Radius Works Good.... What else do I need to know?
How about a longer turnout which can also access the long tender, especially with DCC/Sound... (also accomplished).
In my not so humble opinion...
This is the correct direction for the NMRA:
Just chagrinned to say....
These NMRA Specifications (Class Q) were not published until AFTER, I had already decided to begin to adopt Prototype Standards in 2015.
Only took me 50+ years of Model Railroading to begin to see the light.
I found myself saying...
Well first off they are not Toy Trains...I endeavor to model a railroad, using BNSF Specifications.
Mighty Tall Talk for a guy who has 22 Totes of Model Railroad Supplies stacked-up in his Covered Patio...and not yet put into use on a Layout.