Unfortunately yes. A car or even a truck is standalone and its frame only has to account for the forces of itself moving and crash absorbance, whereas a railway car has to be able to withstand the pull and push forces of dozens of cars - the most basic train has one locomotive at the front and each car must be capable of transferring the entire pull force that the first one behind the locomotive gets, which is for European railways usually anything between 200 to 700 (MTAB IORE) kN.

And the only way to achieve that capability is lots and lots of very thick steel.