I think the key to the whole thing might be buried towards the end of the article: "Students began to go without hats as a sign of status". Is it not likely th

I think the key to the whole thing might be buried towards the end of the article: "Students began to go without hats as a sign of status". Is it not likely that as car-owners began to shirk hats - and presumably they would have been more affluent - hats were increasingly worn predominantly by poorer people? Not unlike a tan was originally considered unfashionable as it meant you had been working in the sun? I bet you could find other examples that confirmed that this was a fashion driven by lifestyle changes amongst the upper-middle class.