I think it was a collective socially-conscious (or unconscious) thing. Men in the late Renaissance Age carried rapier swords as a mark of gentility and to show they were of that cavalier-warrior class. As warrior-chivalry separated itself from day-to-day life and warfare was monopolized into a professional arm of governments, the practical fighting rapier was replaced in the 17th and 18th Centuries by a decorative long and thin "small sword". In the early 19th Century, gentlemen stopped carrying small swords and started carrying canes instead. By the Victorian era, gentlemen swapped their canes for umbrellas. The Victorian gentleman carried his umbrella everywhere, rain or shine. The two world wars leveled society somewhat and caused a general backlash against the notion of the dandyish gentlemen. I think it became more fashionable to appear to be of the common middle class and carrying an umbrella everywhere (except in the rain) went out of style. But I think it was the baby boomers’ hatred of all forms of masculine refinement (no matter how practical) in the US that killed the umbrella the same way they killed the tuxedo, martinis, and neckties. Over the years, umbrellas have somehow come to be more and more associated with effeminacy as dumb as that sounds.