Rainy days usually mean crashing into other people brandishing massive umbrellas, large enough to fit an entire obese family under, yet being used by only one person. These collisions usually cause droplets of water to fall everywhere, often splashing onto your clothes and skin. Kind of defeats the purpose.
The Polite Umbrella accounts for other people’s ostentatious overly large umbrellas. Pull the yank string and your umbrella temporarily collapses around you, allowing you to squeeze past others.