> Exactly, and you need rolling resistance for traction.
No, you don’t. Look at e.g. gears: almost no friction, perfect traction.
> Which is why you don't ship hay on trains
No. You don’t ship it on trains because that is uneconomic. You keep your cattle close to your hay producing fields, where they can also graze.
Also, by your reasoning, an empty train would not be able to move?
Exactly, and you need rolling resistance for traction. The heavier the load, the lower resistance you need, and vice versa, because the weight of the load increases resistance. Which is why you don't ship hay on trains, and don't ship iron on trucks.