The machine tools that we all have in our shops, match in function at least those that were used in late 19 and 20th century's. It is therefore much easier to make models of those products with the tools we have. The exposed parts the move add the the drama of the model, Form, Motion, Sounds, all play together to create interest.
Turbines were build in the beginning of the 20th century on manual machines like ours. The Titanic had one steam turbine, a football shaped metal box, with pipes , valves and a shaft. And 2 three story tall triple expansion engines with Rods,levers, Gears, pistons, all moving in a choreographed sound and movement. It would surely be a sight few alive today have ever seen, which also may add to the mystic of reciprocating steam engine.
Modern materials add little to modelling, most any plastic cost more per pound than the types of steel most use, and often more than the cost of AL. Ti is nice but small machines have issues working it, and it cost $20 a pound, even scrap is expensive. The copper based brass and bronze, traditional material for models, is pricey at $8 pound. It machines easily and looks good, I just hate paying the price, but there is little choice.
Stuff like carbon fiber is a engineered material, it is applied in a certain way to handle the loads it is designed for. if the load is applied in a direction that it was not designed for it fails. Having used CF tape and Rods in model aircraft, I know how strong the stuff can be. But they need to be made for the application.