After reading this thread it seems that there are more Pullmans available than first thought. I have the set of Pullmans from the 90's Commodore Vanderbilt set, and I have always admired them. Silhouettes don't both me (after all, at this age I'm just a shadow of myself anyway). They are sturdy, well made and heavy.
I would think that passenger sets that match the cars to the engine would sell better. Also, making cars that you can run with any road name would be a disincentive to a manufacturer.
Alan