Why doesn't someone, like maybe Walthers, make good quality SP and UP Harriman cars - both commute and regular passenger/mail - it seems like Myopia. They keep making the same repetitive junk over and over that everyone else has made/continues to make.
I can add some insight to that.
First is that about 10 years ago they did a massive survey and canvasing of the MR community. The results of that survey indicated that people were sick of constantly modifying Rivarossi cars and the RTR passenger was grossly under manufactured and served. As a result they started their current line. It basically put the Branchline heavyweight kits out of business.
Second. Last September I was entering a 900 square scale foot diorama model contest and choose to use a passenger car in it. obviously a full passenger car could not fit into 900 square feet, so I had to cut it. I choose a Walther's sleeper that was on sale. When I went to cut it, I was expecting something like a Rivarossi or Bachmann plastic tube. What I found was quite different and explains a lot. The Walther's design is basically an open frame plastic crate. The crate has notches and holes at strategic places where different roofs, sides, floors, undercarriages, and end pieces can be attached. So as long as a passenger car has the same wheel base and end-to-end length all they have to do is manufacture a new side with different window patterns and a different interior floor plan and TA-DA a completely "new tooled" car. That is why they can knock out new Pullman standard and ACF cars so quickly. Seems like there current 4 sizes for streamlined and 2 frames for heavyweight will last them for years and at least 30 more "named trains" before they really have to re-tool for something new.
And I hardly call what they are doing repetitive junk. They are making unique cars which many modelers including myself have only dream't about someone making for years. One of them in this current set is the Strata-Dome. A car that defies kit bashing or scratch building as the web-work in the dome is so intricate. Before that it was the Hiawatha skytop observation and full dome. A few sets ago there was the UP dome-diner. Before that the GN big dome and coolie observation. I still can't wait until they do the NP 310 series sleeper domes. I attempted to kitbash some of those about 20 years ago that came out poorly.