I can’t help but be amused with questions like “Why doesn’t…?” or “Why did…?”
It’s actually pretty simple. They didn’t because: A. They didn’t think of it. B. They don’t think they could make enough money back to cover the investment. -or- C. Someone in power at the company really hates the idea… Conversely, they did because: A. Somebody with a lot of clout thought it was a good project. B. Enough folks asked for it - or- C. a really vocal minority annoyed them long enough that they finally gave in…
Folks new to large scale, especially those coming up from the smaller scales, may not realize how small of a niche our hobby really is. Even worse, it’s further fragmented into half a dozen or so mostly incompatible sub-markets… In other words, it should be surprising how much different stuff is actually available already.
For those still in the 1:24 and 1:22.5 niches the simplest way to get a “new” model is to do a cab and tender swap. A Bug Mauler cab goes on a c-16 rather easily, or on a Connie with a little more work. A c-16 cab on an Indy takes it from mongrel to pretty darn handsome. The c-16 cab will fit the Aristo 0-4-0 as well. — If you lack the nerve to try it on your own, there are at least a dozen guys on here who can help walk you through it.