Why do model companies do this?

[ham99]

There were so many neat locomotives produced, and no one road ran them all. I model UP because it is our local railroad and my memories are mostly armour yellow and harbor mist gray. And because UP had challengers, Big Boy, and turbines. But I'd love to have an excuse to run a cab forward. And warbonnet paint is very appealing. And shays. And billboard cars for products that came into being after billboards passed on. That's the challenge of developing a layout.