Anything that has wheels requires a suitable surface beneath it. This is why in Mesoamerica wheels were known but only used in toys - the terrain was not suitable to good roads. And the smaller are those wheels, the smoother it has to be. And those suitcase wheels are small.

So far it is well known facts. From this conjecture. In the 20th century there is a certain - international - push to make cities wheelchair and baby pram accessible. So the surfaces are more and more suitable for rolling. Minimum wage laws and rising leading standards leading to porters disappearing.

The inventor cites changes like more women travelling alone, on business as well, men less likely to play macho with heavy luggage.