Why do trains run on steel rails instead of ordinary roads?

Answer: Steel wheels roll on steel rails with very little friction

The rails carry electricity that powers every train — Many trains burn diesel and draw no power from the rails, and most electric trains get theirs from overhead wires. The rails are there mainly to cut rolling friction and guide the wheels.

Steel wheels roll on steel rails with very little friction ✓ — A hard steel wheel on a hard steel rail barely flattens, so rolling wastes little energy; per ton, a train needs only a fraction of the force a truck does. The rails also guide the wheels, so one locomotive can pull a long line of cars.

Magnetism between wheels and rails speeds them up — Ordinary steel wheels and rails use no magnetism to go faster; only special maglev trains float on magnets, and they don't run on regular rails. The advantage of rails is low rolling friction.