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People credit Dick Fosbury for inventing the modern high jump approach https://en.wikipedia.org/wiki/Fosbury_flop but it was the switch from jumping onto foam pads rather than into a pile of sawdust and sand that made it possible.

how come they didn't raise the platform and put "pillows" on it? :o

This. What held up wheeled luggage was the difficulty of having small, reliable wheels that could bear a lot of weight. You could have big wheels, but that would be impractical here, though not for chariots, wheelbarrows, pushcarts, or rickshaws ... which did exist in antiquity.

I remember metal skates (steel perhaps) in the early seventies.