They are a part of the Japanese urban landscape. I saw the umbrella cover dispenser everywhere, outside restaurants, cafes, shops and hotels. Today was a rainy, cold day, which means that I was able to see them in action. A small number of Japanese people even kept the cover and reused them when they take the train.
I do not know why we never thought about implementing a similar concept. It really comes handy for everyone: you, the shop owner and the other patrons since your clothes and the interior of the place stay dry.
Another popular option is the umbrella locker where you leave your umbrella outside on a special rack. Some versions have locks to secure your umbrella while you go inside. The locked rack is frequently used by hotels to distinguish between the ones that they can borrow from the hotel and the umbrellas that belong to someone.
Watch my short video to see what it looks like.
I concluded after experiencing my first day of rain in Japan that a clear umbrella is a must in Japan. They are so many people that the transparency helps you to not bump to anyone.
Note: I share more videos and photos about my adventures in Japan on my Facebook page.