Nothing weird about it. Early 20th century clothes would have been expensive, made in the UK and probably natural materials, not cheap overseas polyester.
I've two boys DS1 never wears shorts killed 10 pairs of school trousers in P1 and that was me refusing to buy more after Easter going for the least holy of the bunch!
DS2 refuses to wear trousers, much happier in shorts even in winter. They never seem to wear out.
So shorts are cheaper, less material, last longer, it doesn't really matter about the length, same as girls skirts if they fit on the waist then they are all good.