Why? A company could always have ordered a new small batch of molded parts, and machine shops exist to build whatever plans you give them, or just take the worn or broken part and make a not broken part to match.

Moreover, most of the parts on a vehicle like this are going to be metal shafts, gears, barrings, ir panels, upholstery, etc… Not the small, highly intricate parts 3D printing excels at.

3d printing isn't magic lol, you still need to put in substantial time redesigning parts, and 3d printed (at least fdm) parts are way weaker than injection molded ones. they also cost a lot more money per part.

electronics and large metal parts like bogies are also definitely not 3d printable.