Some Japanese trains only stop very briefly at intermediate stations, so having less luggage also makes it easier to get off quickly. We had a close call when alighting at a tiny station and were glad our large case had been sent on ahead! (Turning around at the next stop would have been painful, since it only had one train per hour).

I had to do the latter once in Germany; there was plenty of time to alight, but everyone had piled up their luggage and were picking it out via an O(n^2) algorithm :(