I like the Perpetuum Loco which is a creative version of Electric Locomotive. So I guess to add a creative version of Steam Locomotive.

Idea:
When user putting creative Steam Locomotive, it has already full-filled water and fuel, so user just only select Running to start the steam or Idle to just burning to eliminate steam only. If user click Shutdown, steam locomotive will stop burning but still full-filled water and fuel.

but why?

The Perpetuum locomotive is not an Electric Locomotive. It just never had a new model created for it.